Molly Shannon is best known for her outrageous “Saturday Night Live” impersonations, but the woman behind Mary Catherine Gallagher impressed Sundance Film Festival audiences with her subtle, serious turn as a woman struggling with terminal cancer in “Other People.”

The film, a dramedy about a gay man (Jesse Plemons) who moves home to Sacramento to take care of his mother (Shannon), kicked off the 32nd edition of the Park City, Utah festival.

As the credits rolled on the film, loud sobs echoed across the Eccles Theater, as many members of the crowd stood and cheered for first-time director (and “SNL” writer) Chris Kelly as well as his cast — including Bradley Whitford and Maude Apatow — and producers Adam Scott and Naomi Scott.

Kelly revealed that the story was mostly autobiographical. “This is sort based on my life,” he said. “When trying to cast this movie, I wanted funny people. That’s what I remember — death isn’t just sad all the time.”

He noted that there are humorous moments even when watching a loved one grapple with a debilitating illness.

“There’d be this horrible, sad, depressing experience and then my mom would be like, ‘I just got done trying medical marijuana,” said Kelly.

Shannon drew the loudest applause as she took the stage and the buzz in Park City is that the actress could get some awards attention if the right distributor picks up the film. During the audience Q&A, Shannon talked about how she started her career as a dramatic actress studying at NYU, and had to catch her breath after reading the script. “It’s just so touching when someone pulls straight from his heart,” she said.

A stream of older audience members left mid-way through the film, perhaps because of its frank depiction of sex between two men, but part of “Other People’s” charm is that it’s the rare movie that features gay characters as three-dimensional figures. Plemons character David is unable to connect with a father (Bradley Whitford) who refuses to accept that his son is gay.

“This is as much about loss as it was acceptance,” said Plemons.

Another scene-stealing performance is from 14-year-old J.J. Totah, who plays the flamboyant younger brother of one of David’s hometown friends and stages a drag dance show for his neighbors. Totah said he helped developed the character with Kelly, including his character’s obsession with carrara marble. “My character is unique and comfortable with himself,” he said, when an audience member noted he’d never seen anything like him in a movie before. “Use color and paint a picture, honey. That’s what we should all do.”