BOSTON — When the film ended and a spotlight shone on him, Boston Marathon bombing survivor Jeff Bauman turned to actor Jake Gyllenhaal and asked, “What do I do now?”

“Stand up,” Gyllenhaal said, and when Bauman rose on his two prosthetic legs, he saw more than 2,000 people in the Toronto theater turn toward him in a standing ovation.

“I think it was because they saw just how hard it was for him to get there,” said Gyllenhaal, in an interview at The Four Seasons Hotel to promote the film “Stronger,” which opens Sept. 22. “It truly was one of the most special moments of my career.”

As Bauman, Gyllenhaal takes a challenging, painful journey, beginning with the fateful decision to cheer on his former girlfriend at the finish line. His private tragedy became public when his photo — sitting wounded and stunned in a wheelchair pushed by rescuer Carlos Arredondo — went viral. Within a day, the media and public started calling him a hero after he regained consciousness and gave police identifying information that led them to find the Tsarnaev brothers.

“I don’t think I’m a hero,” said Bauman, sitting next to Gyllenhaal during the interview. “I consider the first responders and the caregivers and my mother the heroes.”

That identity tension propels “Stronger,” which explores not just Bauman’s recovery from his physical trauma, but his emotional, psychological ones as well. Rallying around him, his mother, Patty, played by Miranda Richardson (“Harry Potter”), and former girlfriend, Erin Hurley, played by Emmy-winner Tatiana Maslany (“Orphan Black”), undergo their own transformations as they struggle to cope and support him.

As Hurley tells Bauman during an argument, “This didn’t just happen to you.”

Filming the bombing at the former South Weymouth Naval Air Station, director David Gordon Green (“Our Brand Is Crisis”) recreates the April 15, 2013, attack in which three people were killed and more than 260 injured, that still shocks, despite its familiarity. But then he takes audience members to places they’ve probably never been.

“He was a normal guy, and I was inspired by the story of hardship, hope and healing,” Green said. “And then I wanted to explore the situations that were in the shadows.”

After he read the script — based on Bauman’s memoir, Green knew he wanted Gyllenhaal to portray him. Before the bombing, Bauman was a seemingly happy-go-lucky, 27-year-old Costco meat department employee. Living in an apartment in Chelmsford with his mother, he hung with his salty-mouthed friends and relatives in a neighborhood bar and was desperate to win back his girlfriend, who had tired of his boyish unreliability.

“I knew Jake had the playful quality of Bauman and would dedicate himself to a story this complex,” Gordon said.

Banter, jokes, and put-downs among Bauman’s friends and relatives provide the movie’s humor, much of it improvised.

“I tried to create an environment where the characters would feel real and raw,” Gordon said. “Given the struggle, I had to make sure there were light-hearted moments.”

Some of the most powerful scenes were filmed in Boston’s Spaulding Rehabilitation Hospital, where Bauman shrieks in pain as the nerves of his amputated legs come into contact with the mold for his prosthesis and as he sweats during therapy to strengthen his core to enable him to walk.

“Understanding his pain was a big challenge,” Gyllenhaal said. “I’m most proud of showing what it took to walk and when someone who has gone through something like this says, ‘This is what it was like.’”

More than his portrayals of fictional characters, Gyllenhaal said he felt an immense responsibility — imposed by himself and others.

“I felt like a bit of a fraud, coming in,” said Gyllenhaal, 36, who spent days doing research and being with Bauman. “I got a lot of ‘Oh, you better do a good job.’ But I think that pressure made me work harder.”

In much of the movie, Maslany is as compelling as Gyllenhaal. Filled with guilt that Bauman would not have been injured if she hadn’t been running, Maslany gives up her job and devotes herself to helping him heal and to advocate for him when he is overwhelmed by the devoted, but not always helpful, involvement of his mother and relatives. She has moments of great anger and frustration, but her love grows for him as she becomes his confidant, nurse, and lover as he copes with post-traumatic stress disorder, self-doubt and despair.

“She’s struggling to figure out her role in his life,” Maslany said. “It’s very relatable. The thing that is so beautiful is that you realize that everyone struggles with ‘How would I rally, how would I take care of someone?’ It’s really about relationships.”

Now a mechanical engineering student at Middlesex Community College and divorced this year, Bauman lives in Carlisle and remains friends with Hurley, with whom he shares custody of their 2-year-old daughter, Nora. While he once was, as Hurley criticized, someone “who doesn’t show up,” Bauman has developed the maturity to match his big heart, Gyllenhaal said.

“Now, he says, ‘I have to leave to pick up Nora on time,’ and ‘Get me a Pellegrino, not a beer. He’s handled an impossible task with grace.”

Bauman, who doesn’t seek publicity, nonetheless is pleased that people around the country will know his story.

“People will see a lot of battles in my head and the connection between everyone around me, and that’s what I love,” he said.

— Jody Feinberg may be reached at jfeinberg@ledger.com or follow on Twitter @JodyF_Ledger.