After he was recently asked to gather his thoughts for an article for Talkhouse, Luke Lorentzen was flipping through the pages of some journals he kept during the making of “Midnight Family,” hoping to jog his memory about how exactly he wound up in the back of an ambulance run by Fernando Ochoa and his sons Juan and Josue, racing around Mexico City in the dead of night on emergency calls.

“The first thing that I saw was Fernando’s phone number that he gave me when we first met and it just brought back this overwhelmingly potent feeling of happening upon these people and not knowing anything about them other than they have an awesome ambulance,” laughs Lorentzen, remembering the description that could be considered crude both in its casually scribbled form on the page and accurate yet woefully inadequate to suggest the three years that he would spend following the trio into life-or-death situations.

That immediate sensation that Lorentzen felt is actually one that’s sustained over the pulse-pounding 81 minutes of “Midnight Family,” which sees the Ochoas overwhelmed by 911 calls where they are just one of 45 ambulances in a city of nine million and without a strong public health care system in place, medical transport has become an unforgiving business where the patients don’t know if they’ll get to the hospital on time and the drivers can’t be assured they’ll get paid when few have insurance or other means to pay. Requiring tips from cops to get a leg up on the competition becomes another out-of-pocket cost for the Ochoas, who are first concerned with the care of victims of car accidents or domestic incidents they attend to, yet have to keep their eye on the bottom line when they are reduced to limited meals a day of canned tuna.

While that underlying tension gives “Midnight Family” a crackling energy, Lorentzen channels the exhilaration that the Ochoas can feel answering a call, opening up the frame to the point where it feels like each scene is pushing its way out of the screen and the whir of sirens become an extension of the emotions churning inside. The filmmaker renders the experience so viscerally stimulating you almost forget to breathe, but still leaves plenty of room to think about the failures of a system where money has become a greater incentive for health care than human compassion and as impressive as “Midnight Family” is as a one-of-a-kind nonfiction thriller, it leaves its mark well after it ends as a ground-level view of societal issues that rise right to the top. With “Midnight Family” now in theaters after a celebrated festival run that began at Sundance earlier this year, Lorentzen spoke about operating largely as a one-man crew and how he used time to find the best way to capture the experience he had in the Ochoas’ ambulance for this unforgettable film.

I understand the story found you instead of the other way around.

Yeah, I think that’s a good way to put it. I moved to Mexico City just a few days after I graduated and I went just with a friend that I was living with in college who grew up there. He was moving back home and encouraged me to come check it out. I was 23 years old and just looking for fun and in my first month there, the neighborhood that I lived in was the same neighborhood the Ochoas worked in, so I would see them pretty regularly. I was looking for different film ideas and I built up the courage to ask them what they were doing with their ambulance and if I could ride along for a night to see them work. And in that first night, I was just totally blown away by what I saw. Pretty quickly, I decided I should be going on rides with them as much as possible and over the course of three years, I spent really large periods of time filming everything they did.

What was the gestation period like, figuring out you wanted to pursue this as a feature? Was there any time you spent with the Ochoas without the camera?

I didn’t spend any time with them without the camera there and I try to start off from a point of “I’m a filmmaker“ instead of I am a person because then I feel like if you introduce later all of the things you need to do to make a film, it creates an awkward shift. That doesn’t mean that I was always filming. I tried to be a presence that they liked having around and the process of building trust is like how do I convince these people that having me here is better and more fun than not having me here? And whether or not the camera’s in my lap or not, it didn’t always matter. I thought it was maybe going to be a short or a capsule in this larger idea that I had, but then it grew and grew and within a month, I knew it needed to be its own feature.

But I had a really specific concept for from the very beginning. In the first week, I knew that I wanted to show five or six accidents where in each accident, the ethical stakes grow. But it took a really long time to get the material and to build the relationship and build the skill set as a filmmaker to follow through with that initial idea. The whole process of making this film was so fluid in that I was learning how to make a movie, I was learning this whole new world that was foreign to me and there was this constant push and pull of wanting to be flexible and bendable to the world around you, but also wanting to have a directorial voice and have a vision, which happens on every project I work on, so it was a very circuitous and nonlinear pathway to the point that I had started at to the idea that I started with.

One of the bold choices upfront is the Prime lenses and the wide frame, which seems counterintuitive to how most would’ve shot inside the ambulance. Did that come immediately?

One of the things that really saved me was that the Ochoas would kind of do the same routine every single night, so that repetition gave me so many chances to try things that didn’t work out without losing the whole story. On some nights, I was like, “I’m going to try this lens, I’m going to try this camera and see what happens.” And little by little, I built up a camera package and then ultimately a look for the whole film that I could follow through with. I was able to make some really bold decisions in terms of how I was going to shoot the film because I learned the spaces that all the scenes would unfold in really well. Anything could [happen] in the back of the ambulance and I had already shot it 10 or 15 times before just because of how repetitive the work was. I wasn’t following the Ochoas into spaces they hadn’t been before and I was trying to really control what was on the table and what was a possible shot that would be in the film so that it ultimately would have a really cohesive look and feel.

What was it like approaching the Ochoas with questions? I realize during one scene with Juan, he must be exhausted from the day he had, but there was likely no other appropriate time to talk.

Yeah, there’s only two really brief moments in the whole film where I’m asking them anything [since I wanted] the film to really stand up without any interviews or voiceover or those sorts of devices. Both of those moments play out like these monologues more than like a direct interview and they came really late at night when we were super-bored and just chatting away because every time I tried to set up an interview [with Juan] or more explicitly set something up to talk about his work, I didn’t get anywhere. It was always these really late, almost half-asleep moments where we were laying down in the back of the ambulance chatting and I happened to get a frame that worked.

You learn a lot from just hearing him talking to his girlfriend on the phone.

Yeah, that was such a goldmine for me as a filmmaker [because] after any big event in his life happened, the first thing he would do is he called Jessica to tell her about it, so I had these reflective bits that would come and help me explain certain things that happened. And she’s someone I never met in spite of having spent so much time with them. [laughs] He talked on the phone constantly, but he would always leave his family to go see her on his day off on Monday and I never went with him. I should’ve. They had a baby together right after we wrapped shooting.

Wow. Was there a particularly crazy day of filming on this?

Every day was unpredictable. I think what was so emotionally draining is you’re sitting there in this ambulance waiting for hours and you almost begin to hope something will happen just because you get bored. Then the moment something does happen, you fear what it will be, so you’re pulled between this mundane, exhausted boredom and this hyper-stimulation in every possible way. Even when you start to feel comfortable in this ambulance and see such a wide spectrum of things, you’ll show up to something that will surprise you in ways you cannot even imagine. It’s such a hard line of work and it takes every little bit out of you. I’ve been lucky to leave that space and take a breath and reflect and process some of the things I experienced, but these EMTs like the Ochoas are doing it every single night are getting pounded with emotional exhaustion in ways that I don’t even think they’re fully able to process and think through.

What’s it been like to travel with the film and see them recognized for their work?

It’s beyond anything I could’ve hoped for. We were able to bring the Ochoa family to the premiere at Sundance, which was just an incredible moment. They got a standing ovation in front of this 600 or 700 person audience and when I was making the film, I was really cautious about not sugar-coating how complicated and dark this business is, but I also really care about the Ochoas and I was able to see that dynamic play out as I hoped in that screening where people were empathetic to them in spite of their flaws. And since then, the film has gone to 130 or 140 festivals around the world and I’ve just been hopping from country to country showing the film and it’s been amazing. It’s been truly incredible.

“Midnight Family” opens on December 13th in Los Angeles at the Laemmle Royal and San Francisco at the Roxie Theater. A full schedule of cities and dates is here.