Patty Duke died Tuesday. She was 69.
Credit: Rob Latour/Invision/AP

Sean Astin has paid a touching tribute to his late mother Patty Duke, who died Tuesday. She was 69.

In a statement on his Instagram account, Astin wrote: “This morning, our beloved wife, mother, grandmother, matriarch and the exquisite artist, humanitarian, and champion for mental health, Anna PATTY DUKE Pearce, closed her eyes, quieted her pain and ascended to a beautiful place.”

Astin, 45, – star of The Goonies and The Lord of the Rings film series – has also started a CrowdRise initiative, titled the Patty Duke Mental Health Project, to honor his mother, who was diagnosed with bipolar disorder in 1982.

Astin calls his mother a “tireless warrior” in his tribute on the CrowdRise page, detailing how she campaigned and lobbied for mental health awareness, which he now wants to continue.

Speaking to Good Day LA on Tuesday, Astin spoke about how the campaign, which has already raised over $22,000, is helping him deal with his loss.

“I feel rock solid at this moment because I m charged with a sense of mission for her,” the actor said. “So, it’s great to have purpose. There’s some things in her life that she d like to continue after her, and we talked a lot after that. The moment of someone s passing, particularly a public person, generates a pulse, so I just want to honor that.”

He continued: “At that time in the mid-80’s, when she ‘went public’ with her diagnosis and sharing her story about her mania and her depression and all that. I don’t know how many actors or celebrities had, kind of, done that. I go around and give speeches on this kind of carrying the torch for her and stuff, and I would say that the world now is infinitely more understanding and compassionate, and yeah, there’s still stigma, but it’s a different world out there. And, I think she had a nice role to play in that evolution of our society, so we re all very proud of her for that.”

Duke sat down with PEOPLE in 1999 to open up about her battle with manic depression and reveal how she turned her life around.

Astin told Entertainment Tonight that Duke was “surrounded by her family” in her final moments, after relatives traveled to her hospital bedside in Idaho. And after a lifetime of overcoming obstacles, Astin said his mother was finally “at peace.”

“When it was over, we all looked at each other and we thought, you can be an atheist, a skeptic, agnostic, you can be whatever you want, but what just happened in this room is indescribably beautiful,” he said.

And while Duke’s legacy will live on through her acting career, her son notes that her “true story” centers around her ability to love.

“The true story of her life isn t her work and it isn t her advocacy, it s the love relationship she s had with her husband Mike [Pearce] for the last 30 years,” Astin told the Associated Press. “He was a drill sergeant in the Army when they met and he became her 30-year project, and she finally in her life had a protector. And so she showed him the world and he took care of her and until this morning at 1:20 they were connected with a bond that is impossible to describe.”