Jeremy Richman was discovered by an electrician in Newtown, Connecticut's Edmond Town Hall the office building where he worked on Monday morning, police told CNN .
Richman's daughter, Avielle Richman, was one of the 20 children killed in the Sandy Hook massacre in December 2012. Six educators were also killed.
His death comes after two survivors of the Parkland shooting died from apparent suicides in the last two weeks.
Police said they "will not disclose the method or any other details of the death," but said it does not appear to be suspicious.
US Sen. Chris Murphy, who has been an advocate for stronger gun control laws since the Sandy Hook shooting, said on Twitter that Richman was pushing for more research into violence triggers in the brain.
"My god. This is awful, horrible, devastating news. Jeremy was a good friend and an unceasing advocate for better research into the brains violence triggers. He was with me in my office two weeks ago, excited as could be about the Avielle Foundation's latest amazing work," he said following news of Richman's death.
Gov. Ned Lamont expressed condolences to the Richman family in a statement to the Courant.
"Annie and I are heartbroken for the Richman family. Thoughts and prayers just dont feel like enough in times like these. Words cannot even begin to express our sorrow," he said.
Richman was a scientist and a mental health advocate, and he and his wife, Jennifer Hansel, founded the Avielle Foundation to push for brain science research following the Sandy Hook shooting.
He left his job as a researcher at the pharmaceutical company Boehringer Ingelheim to focus on work with the foundation, which had an office at Edmond Town Hall, an event space in Newtown.
