Dotdash Meredith and Yahoo Inc. may earn commission or revenue on some items through the links below.
James Tupper is proud of how his son is faring amid a "very difficult time."
Speaking with PEOPLE at a reading of Anne Heche's new memoir, Call Me Anne, the late actress' ex — with whom she shares son Atlas, 13 — commended the teen's beautiful remembrance of his mother, shared on the book's release date.
"I asked him if he wanted to say something... I had explained to him what the situation would be and he went into his room for an hour alone and came out and said, 'This is what I want to say,' " Tupper tells PEOPLE. "It was very affecting to me, very beautiful. But what he wrote was very beautiful. It's straight from his heart."
Atlas remembered the late actress as "the brightest person I've ever known" in a touching tribute published on Tuesday.
"She always knew how to solve a problem, or help a friend," he said in a statement shared with the Los Angeles Inquisitor. "She always knew the right thing to do. I cannot put into words how grateful I am or how much I miss her."
Never miss a story — sign up for PEOPLE's free daily newsletter to stay up-to-date on the best of what PEOPLE has to offer, from juicy celebrity news to compelling human interest stories.
RELATED: All About Anne Heche's 2 Children
As for how he and his teen son are coping with the loss, Tupper tells PEOPLE, "Atlas has taken up tennis so he plays like two to three hours a day, and I think that's creating a real nice balance."
He adds that Atlas "has really good friends. So keeping these things carefully in balance, that's how we're getting through grief."
Tupper says that "looking after" Atlas through this "very big transition" has been his "whole focus" as they navigate the aftermath of the actress' unexpected death on Aug. 12 at the age of 53.
"I want to say that I'm doing great, but it's been a very, very difficult time. A very big transition and spending time with my boy and looking after him, that's basically been my whole focus," shares Tupper, who dated Heche from 2007 to 2018.
"It's very difficult whenever you lose a parent like that. Your whole world switches inside out, and I think kids experience trauma in a way that adults don't. Adults have a context to put it in, but kids do not. You want to bury it, you want to forget about it and move past it," he adds. "I happened to have lost my mom, too, when I was very, very young. So I kind of understand what he's going through."
"He's got great support around him, loving friends and family," Tupper adds of the teen.
Earlier this month, Homer spoke about the book and announced the "special" Barnes & Noble event in a post on his mother's Instagram account. The actress had been writing Call Me Anne, her follow-up to 2001's Call Me Crazy, for months leading up to her death.
"I have a responsibility to share with her community what she was working on and how excited she would have been to tell you herself," he wrote, in part. "The book is the product of mom's further efforts to share her story and to help others where she could. Call Me Anne is the result and I know she was excited to share with the world."
"So, mom, here I am sharing it with the community you created, may it flourish and take on a life of its own, as you would have wanted," he added. "I know mom would want to see everyone's smiling face as she read an excerpt and signed copies."