When filming was complete on “The Heart of Nuba,” Kenneth Carlson thought the hard part was behind him. In making his way to film at the Mother of Mercy Hospital in South Sudan, he had dodged bombs and gunfire that had become a part of everyday life in the region where a civil war continues to rage on between local rebels and the federal government led by Omar al-Bashir. ‎But for the effort, Carlson, who previously made the well-regarded high school football documentary “Go Tigers,” was dismayed to learn when he returned to America, there were few interested in what he uncovered, at least amongst the gatekeepers of festival programmers.

“Initially, it was tough,” says Carlson. “I’d done all of this and risked my life and was met by some rejection by the festival, ‎and they didn’t know how to program us.”

It had become a good thing then that Carlson had become accustomed to hearing “no” during the filming of “The Heart of Nuba,” growing a thick skin from the start of filming since it took quite a bit of convincing for even the film’s subject Dr. Tom Catena to agree to make it. Even after arriving safely at Mother of Mercy, Carlson was aware his longtime friend could be immovable after the two had been teammates on Brown University’s football squad where Catena had been a nose guard, but that’s what made his story so compelling. Catena’s steely determination didn’t only make him a force to be reckoned with on the gridiron, but off of it as well as he followed his religious calling to set up his medical practice in the Nuba Mountains where the Catholic Church opened up the Mother of Mercy clinic to serve the million people who live there. Serving the community for all of its medical needs, be it as a surgeon, a physician or the local gynecologist, he treats patients for every kind of malady there is, including diseases that have long gone extinct in the West such as leprosy.

As the only one in the Nuba Mountains with these skills, Dr. Catena is quite singular, though he works to train his staff to broaden their abilities. But he’s unique in another way, keeping a patients’ log that can be read as evidence of the war crimes committed by President al-Bashir. In relaying this testimony, “The Heart of Nuba” becomes a valuable eyewitness documentation in its own right, not to mention a compelling one as Dr. Catena continually has to wonder whether it’s the sound of wind or a fighter jet flying over his hospital, and like its brave subject, the film has found a way to relay the plight of the Nuban people to the rest of the world, despite all odds, arriving in theaters this week. On the eve of the release, Carlson spoke about navigating treacherous terrain to make it, making a film about a friend in great peril at all times, and how the film has been able to affect change even before the general public has had a chance to see it.

Dr. Tom Catena in "The Heart of Nuba"What was it like to make a movie like this from the perspective that you have, knowing Tom first in completely different circumstances than the person he is today?

First of all, you’ve got to know that Tom Catena did not want this to happen. I met with him in New York [when] he came out to receive an award, which he ultimately utilized to get in front of the U.N. to pitch them on bringing U.N. forces back into the Nuba Mountains. When I pitched him the idea of doing a film about him, he said, “Absolutely not. No one cares [about me], and I don’t want the attention.” So I had to really convince him to make a film about the conflict there and he said, “If you come out to Mother of Mercy Hospital and you prove to me you want to make this film, then I’ll consider doing it.” And I showed up and [then] he said, “Alright, if you make a film, I want it to be about the Nuban people,” so you see he’s our narrative throughline, but ultimately by the end of the film, it’s about the Nuban people taking over the ownership of the hospital. He’s very insistent upon dodging the light. He does not want it to be about him. He wants it to be about this conflict and he wants to go about affecting change. He felt like this film would be certainly a way to do that and it has been.

I understand that first day was almost quite literally a trial by fire since you were greeted by guns. Does that actually strengthen your resolve to tell this story?

Yes, that was my welcome to Africa and it was a challenging shoot both times that I went out. That [first day] was actually in South Sudan on my way to the Mother of Mercy Hospital, and I landed there having been on this cargo plane for two-and-a-half hours. I was dehydrated and the pilot said to me, “Hey, would you help offload with me these 50-pound bags of rice, beans and sorghum,” so I said, ‘sure’ and as I’m doing that, I notice that this huge crowd [assembling as] aid was being delivered. We were offloading these bags and there’s this surge of children pushing towards the airplane, screaming and yelling, so I continued to [unload the bags] and then I thought, “What am I doing here? I’m a journalist. I want to capture this.” So I put a 16mm lens on my SLR, stepped back and got this great footage and photos of what was happening. Just then a guy pointed his finger at me and said, “Get off the plane now,” and “bring your camera.”

So I got off and he’s yelling and screaming — starts spitting upon me — and said, “What do you think we are? Just a bunch of fucking moneys here?” I’m like, “Wait a minute, time out. I’m just here as a volunteer for the church.” Then AK-47s came out, [with these] 12- to 15-year-old kids pointing these guns at my head. They interrogated me and I kept on telling them,” I’m there for the church” and they got my cameraman off the plane and brought all of our equipment out, piled it up in the middle of this dirt tarmac and finally after 40 minutes of being dry-mouthed and being beaten down, telling them “I’m staying here, there’s no way I’m leaving,” I finally [said], “Listen, I’m making a film about Dr. Tom Catena.” And they stopped and looked at me and they said, “You know Dr. Tom?” And I said, “Yes,” and seeing that there was a crack in the fissure, I told them the situation about being on the same football team. After another 20 minutes there, they gave me my camera back and said, “You know Dr. Tom. You can go.” So I got back in the plane and the pilot said to me, “Do you know how lucky you are?” I said, “Yeah.” And he said, “No, do you know how lucky you are?” I said, “How so?” He said, “Two weeks ago, this very cargo plane landed here, 26 people were yanked off of it and taken to the corner of the airstrip and their throats slit and left to bleed out.” And I’m just wide-eyed and I said, “Well, get in the cockpit, get those engines on and let’s get the hell out of here.” That was my introduction to that part of the world.

But keep in mind, I went there twice, I got the story and I left. Dr. Tom remains. He does not leave. He’s bombed relentlessly. [To get up to Mother Mercy Hospital], we put mud on the vehicles, dust all over them, so they were hard to detect from the air and sure enough, when the sun came out, Antonov [cargo planes] came over and started bombing us [on our drive there], and when my driver yelled something in Arabic, slammed on the brakes and jumped out, I followed him, got down in a ditch and stared up at the sky. We think they’re about two, two-and-a-half miles away, and it was enough to shake my gut, but not my resolve. You can [usually] hear the gunfight in the distance. It’s harrowing to actually go through it, but [Dr. Tom] remains. He is there not only stuffing envelopes or filling sandbags, he’s there performing some of the most difficult surgeries imaginable. He’s the last line of defense. He provides care and hope for over a million people by doing what he’s doing.

Dr. Tom Catena in "The Heart of Nuba"When he’s performing all that medical work, what’s it like to be unobtrusive in that situation?

[Tom] hated it. [laughs] Tom didn’t want to have anything to do with it and I had to prove to him it was worth doing. I caught him in church one time and chapel service is actually outside, so I came in and was filming at a low angle and just trying to be as unobtrusive as possible and he just looked at me and just waved his hand, like “get away.” It was very difficult and after eight days [of being there], I finally broke him down. He gave me an interview. Keep in mind, this is a buddy. He didn’t want cameras following him around because ultimately it would be the villagers [saying], “Dr. Tom brought this camera in and he’s making a film about himself,” so he was extremely sensitive about it.

Going into surgery, I didn’t go in the first day he was in surgery [while I was there]. I filmed around town because I didn’t want to be obnoxious, but eventually I convinced him that it was the right thing to do. We needed to see him in action and he allowed it, but he was extremely reluctant because it’s a small, tight-knit community and he knows that people talk and that he did not want to change the nature of business there. They live in a harmonious state and to throw that off is a big risk, so he was not welcoming. The people, though, were very curious as to what I was doing with cameras, walking around. There’s a moratorium on all aid workers, journalists, and certainly filmmakers from going in this part of the world, so I entered illegally and it was unusual for someone like me to be there. Tom was even more so restrictive because he just doesn’t want attention. He just wants to do what he considers God’s work and he wants to stay focused on that, so it was difficult, especially in the surgery situations, to make sure I stayed out of his way.

You mentioned two shoots – having the experience of the first, was the second a lot different?

The second time I went in knowing more what I needed – the holes in the story and what storylines I wanted to pursue, the interview questions I needed to ask Tom – so it was with more purpose, but certainly with trepidation because it’s a very difficult part of the world to shoot in. I had three different cameramen that were going to go with me from Los Angeles – that’s where I’m stationed nd each one, when they really did more research, figured out that this was not an assignment for them. I finally found a guy out of Nairobi, someone who didn’t know better. [laughs] And there were only two of us – no sound man, just a cameraman – and I did sound and he did a little bit of sound too, and we went in and for the first three weeks, it was tough, uphill sledding, but the second time I went in, I reached out and said, “I’m going back, I’d love for you to come” and he said, “Hell no, over my dead body. I’m never going back there again.” It just tells you how difficult it was.

I’ve got a wife and three kids and when I came home [from the first shoot], I came clean. I told [my wife] what I was up against and about being held at gunpoint in Turalei in South Sudan and being bombed by Antonovs on the drive up and for me to turn around and say, “Listen, I’ve got to go back,” major props to her for letting me go. Of course, she did take out a huge insurance policy. But she allowed it to happen and my kids were nervous as all get out, but I had to get the rest of this story. Knowing what I know now, I went there more prepared. I had identification that attached me to the hospital. I had laminated photos with me and Dr. Tom together in our football uniforms and in the hospital together that I was able to produce at a moment’s notice. That really helped me pave my path in and out of the Southern part of Sudan in the Nuba Mountains.

A scene from Kenneth Carlson's "The Heart of Nuba"There’s an elegant sequence in the film about a most inelegant time in Dr. Tom’s life, when he gets malaria and you use a window sill to convey what’s drifting in and out of his mind as he faces what could be the end. How did you figure out how to convey that?

Malaria is like you’re taking a hallucinogenic. For [Tom], it happens every year and he doesn’t whine or complain, but he thought at that time, he really was going to die, so we created that and tried to lift stuff from the footage that we had because we weren’t there when he had malaria, so we [had to] take some creative license, but hopefully it gives you a sense of what it’s like to have this recurring illness. This [time] was recounted to me by him and the nurses and by the way, that was two years ago and he’s gone through it twice since then. We’ve also found out he has two forms of tuberculosis because he went up into a tuberculosis and leprosy camp, and as he says in the film, you don’t get it by touching these people, but by respiratory droplets. People cough on you excessively, so he had two forms of TB, he gets malaria all the time and then he just had pneumonia, but this doesn’t stop him. He just keeps going.

At that particular point in the film, we didn’t know if he was going to survive and then he took the time to go back because he realized his father was greatly ill, so he went back to Amsterdam, New York, to see them and it put things in perspective how precious life is. It’s very impactful part of the movie, and that was the first time I reacted emotionally [to the movie myself] – when I saw the first cut of the scene, going back to the family, right after the malaria section, because I really realized for the first time what he was truly sacrificing by going over there [to South Sudan]. He has this amazing family that all love and support him, but he has parents who both aren’t doing well [healthwise], and that was the first time I really welled up, thinking that this guy’s sacrifice is beyond anything I realized. It took me going out there and seeing all of this and then putting it together as a piece that really had such an impact on me.

Dr. Tom Catena in "The Heart of Nuba"What’s the last year been like bringing this out into the world?

It’s been exhilarating. It was met initially with disappointment. I’m an alum of some festivals, large festivals that we all know and are enamored by and I didn’t get in, so that was painful. but I came across a woman named Bonnie Abaunza, an activist who saw the film and said, “I know what to do with this, let me help you out.” She created, along with myself, a human rights coalition of 70 NGOs with the likes of Amnesty International, Human Rights Watch, Act for Sudan, The Enough Project, and they then provided the wind beneath my wings. They embraced the film and we screened the film several times for Amnesty International. People started hearing about it and we screened the film for Congress on Capitol Hill, supported by [U.S. Representatives] Jim McGovern and Michael Capuano, then the House of Lords [where we] played it for the British Pariliament and then we went over to the Italian Senate and the International Criminal Court. All of a sudden, we were screening around the world and festivals started picking it up, so we had success, but we had to prove to them this was worthy subject matter.

We’ve been fighting that uphill battle, but obviously we’re in theaters now and more importantly, I’m proud to say it’s been 13 months now that the film was instrumental in getting a cease fire declared [in south Sudan]. They have been living in peace now in that area because we were able to get the film played in front of the General Omar Hassan al-Bashir, the president of Sudan, so ultimately we are now thrilled that the film has now had an incredible impact and we are working with the government now to create a humanitarian corridor to get aid into these needy parts of the world, the Nuba Mountains and the Blue Nile District. We’ve raised over $300,000 for the hospital thus far without even being in theaters and Nicholas Kristof has written three articles, which have raised over $400,000. And [Dr. Catena] just won the Aurora Prize, which is $1.4 million, and part of that came back to the hospital, so creating awareness like this has really changed the landscape in the Nuba Mountains.

“The Heart of Nuba” opens on April 6th in New York at the Village East Cinemas and April 20th in Los Angeles to the Laemmle Music Hall.