It’s difficult to get through the trailer for Stronger — the real-life story of Jeff Bauman, who became a double amputee following the 2013 Boston Marathon bombing — without being brought to tears. Jake Gyllenhaal plays Bauman on screen and the movie’s poster, debuting on ET, shows him mid-physical therapy with the tagline, “Strength Defines Us.”

Director David Gordon Green tells ET that his film is more than just a tearjerker, though. “You’re in for a ride,” he said by phone. “That certainly expresses a side of the emotional intensity of the movie, but you might be surprised to find a sense of humor woven in there as well. Expect a few chuckles alongside a tear or two.”

ET: The movies you are perhaps most known for — Pineapple Express, Your Highness — are a very specific type of comedy. You have directed dramas before, but this still feels quite different. What made you want to direct this? And what made you feel you were the right choice to do it?

David Gordon Green: I was really drawn to the script. Of course, we know the headline. Of course, we were glued to our televisions and news sources when the incident occurred at the Boston Marathon. And I get very suspect when I hear of a “Based on a True Story” type of tale, especially one that’s heroic. So, you open the script with all those suspicions in mind and here, I just fell in love with the characters. I fell in love with the humanity. I fell in love with the relationship between Jeff and Erin (played by Tatiana Maslany) and the full complexity of that. The universal spirit that I think this story invites is something beyond just the specificity of this incident and more to themes that we can all relate to, the hardships that we experience ourselves or we’ve experiences through other people.

For me, on a personal level, it’s the first film I’ve been drawn to as a grown up, in a way. I think most of the films that I’ve made, you can point to the spirit of my youth within, looking at a movie like Pineapple Express, for example. But this was a movie that I really wanted to put aside that youthful design I think I’ve tried to infuse in other films and say, What’s important about this story? What’s important about these people and the journey that they’ve taken? I asked a lot of questions of myself, and I think the film asks that of the audience as well.

You mentioned being wary of stories of true life heroes, but when you’re working on a movie about a real tragedy, you also want to make sure it’s not “too soon” and that it’s not exploitative. Are those things you ever worried about before signing on to the project or while you were making it?

I would have in concept, but I don’t think [screenwriter John Pollono’s] script touched on my big concern. In fact, it alleviated it, and I felt inspired by it, that the cheese factor didn’t kick in like it does when I’m watching some movies. It felt very real and beautiful and had a sense of humor. It didn’t ever feel like I was being manipulated in the read, and that was the effort of our production, to be able to bring forth performances that can transcend just headlines and really embody these emotions and take people on a journey that does have an uplifting spirit, that does have an optimism about it. At the same time, it’s dealing with harsh realities that are sometimes very difficult to talk about. The production invited a lot of real-life people to participate, from the surgeon that amputated Jeff’s leg, his physical therapist, the Martino brothers, who helped fit him for a prosthetic leg. So, not just Hollywood actors are coming to this stage, but a lot of authentic personalities that had a voice that brought a truth and a dignity to the subject matter.

How closely were you able to work with Jeff throughout this process?

Very close. We’ve gone from a director trying to get facts of his life from the subject to guys that send funny texts and emails, YouTube clips and goofy crap to each other. Because he does have such a wonderful spirit and sense of humor that was really helpful to me and to Jake as well, as we embarked on this journey with someone whose story is very important to us. We wanted to embrace him and be as respectful as we could. And through that, we formed a great friendship that I think expands beyond just that professional relationship.

Jake is known for going deep into research and preparation for a role. Do you know what that involved for Stronger?

Oh, yeah. You can only ask Jake what his true process is, but for me, in on the action myself, it was really amazing. Jeff invited him into very intimate chapters of his life, of how he takes his prosthetic legs on and off. The three of us would literally be on the floor just trying to imagine how you would physically get from a chair to the floor with no legs, like when he doesn’t have his prosthetics on. Then there’s hundreds of pages of research that Jake had done, not just on Jeff Bauman himself, but the world around him — from the events of the marathon to…you name it. He gets very technical and educated to a point where then he can shut the technical side down when the cameras are rolling and really just embody that. It was impressive to watch.

Before casting him, what made Jake the right actor to play Jeff?

He’s actually the only actor I spoke to about it. There’s a seriousness that you can tell he has within every character, but I’ve always really responded to the sly goofiness he has as well. You can see it even in his most serious roles. You can see it in Brokeback Mountain. You can see it in Nightcrawler. And I thought that was a very important thing to be able to bring to a performance that could be heavy-handed and dramatic. It was important to be able to have some levity and from my first meeting with Jake, I knew he was going to be a playful actor that was able to break some rules of acting and go with me on a journey that was going to be both emotional and ultimately uplifting.

I’m also so happy to see Tatiana Maslany in this. She’s such a phenomenal actress that deserves to be cast in everything. What drew you to her and then what was it like working with her?

I was a fan of Orphan Black, like so many people, and was just blown away by her range and the diversity of her performance. You watch that show and you don’t know which one is her. [Laughs] She auditioned for this and when I got her in a room with Jake, it was very clear that there was a strong female character that could not be afraid of her empowerment and not be afraid of her vulnerability, someone who really challenged the expectations of the romantic lead in a movie. I loved the questions and concerns that she had, and the ferocity and the levity that she brings to Erin were very important to making this a balanced, complicated character, because it’s not just your obvious love interest. It was an opportunity for us to find someone and invite them into this emotional adventure.

For everyone involved, was there a most emotional day on set?

Yes, so many. So many. I would say there were two days that I would highlight. One day involving the rehabilitation center in Boston, where we invited a lot of amputees and patients of the rehab center where Jeff actually lived for months. So, to bring a lot of those people — current and past patients of the rehab center, the physical therapists, the staff — to be a part of the movie, it was really uplifting. It was inspiring seeing this state-of-the-art facility with the complexity of people facing various physical hardships and finding those new steps in life. I don’t even know what it’s called, but for a paraplegic within a body suit taking his first [steps] — you see these moments, and we’re just there as a film crew capturing our story and then suddenly we end up being a part of a monumental moment in someone’s life. That’s an experience you don’t forget.

And the recreation of the marathon aftermath. We have a sequence there. Through our respect of the situation and the survivors and heroes of that day, we tried to have a day where you take your time. You’re very patient. It’s very technical, you learn a lot about yourself and you learn a lot about the event and you learn a lot about the community of Boston. And then everybody holds hands, takes a deep breath and goes for it.

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Official Movie Pictures > Stronger (2017) > Posters