'Mass' takes a harrowing look at school shooting aftermath, told from a parents' perspective

You're unlikely to see a more devastating movie this year than "Mass."

The heart-rending drama, which premiered Saturday at Sundance Film Festival, puts you in a room with two sets of grieving parents six years after a school shooting that claimed both their sons. Their reasons for meeting aren't immediately clear as Richard (Reed Birney) and Linda (Ann Dowd) exchange niceties and a houseplant with Jay (Jason Isaacs) and Gail (Martha Plimpton), who reluctantly sift through old family photographs.

At first uncomfortable and stilted, the discussion soon becomes charged as you discover that Linda and Richard are the parents of the shooter. Jay and Gail helplessly, sometimes angrily, probe them with questions about their son and perceived failings as parents: Weren't there any red flags? Was it bullying or violent video games that pushed him over the edge?

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Linda and Richard repeatedly insist there were no signs. At one point, Linda confesses, "The truth is we believed we were good parents, and in some awful, disturbing way, we still do."

All four characters, as well as the audience, ultimately realize there are no answers. There's just a void left by the loss of their kids, and nothing they do or say can ease that pain.

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The nearly two-hour film unfolds very much like a play: The conversation happens in real time and is confined almost entirely to one room. Actor Fran Kranz ("The Cabin in the Woods"), making a confident directorial debut, was inspired to write "Mass" after the high school shooting in 2018 in Parkland, Florida, where a gunman killed 17 students and staff and wounded 17 others.

"I was just overwhelmed by it," Kranz said in a Q&A after the screening. "I was a new parent and ... listening to a parent that day on the radio, I just started to think: 'What is going to happen to this person? Is she going to be OK? And what would happen to me (in that situation)?' "

The cast rehearsed for two days in New York before flying to Hailey, Idaho, where they shot the film before the pandemic.

In Idaho, "I spent a lot of time alone and thought about the loss of a child," said Dowd ("The Handmaid's Tale"), a mother of three, through tears. "I held on to that grief and said: 'This is what it's like. Don't run from it.' " Rather than improvise, "we hoped to stick to the script because it's so beautifully written."

Despite the extremely difficult and bleak subject matter, Kranz believes there is hope to be found at the end of the film as Gail wrestles with forgiving her son's killer.

"Forgiveness is really hard because it requires letting go," Plimpton said. "When Gail says 'I'm afraid if I do this, I'll lose my son,' I really feel that. I have my own things and my own people I need to forgive, but it's very difficult. ... That hits closest to home for me."

"Mass" will have a second virtual screening Monday (10 a.m. EDT) at Sundance.

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This article originally appeared on USA TODAY: 'Mass': Sundance drama explores parents' grief after school shooting