Newtown police said Richman appeared to have killed himself, but did not disclose further details about the death.
After the Sandy Hook massacre, Richman tried to help make sure shootings like the one that killed his daughter wouldn't happen again.
Richman, 49, was found at his office in Edmond Town Hall in Newtown, the Hartford Courant reports.
According to the American Psychiatric Association, "in some cases, a recent stressor or sudden catastrophic event, failure or (loss) can leave people feeling desperate, unable to see a way out, and become a "tipping point" toward suicide".
Richman is the founder of the Avielle Foundation, which he started after he lost his daughter in the tragic Sandy Hook school shooting. "I give Jeremy credit for what he accomplished with his work and his unbelievable strength that grew through the years".
Just minutes after leaving a forum about gun violence in schools, Sen.
Following his daughter's death, Richman had become a force for change.
"My heart breaks for this family, which has already endured so much", he said.
In the years since Sandy Hook, the constant news of subsequent shootings would come as body blows. "They go on to recover and live", she said.
"We certainly recognize the heartbreak that this is causing", he said in a phone interview.
Richman's friend and associate editor of The Newtown Bee, John Voket, tells Here & Now's Robin Young that Richman was "a source of light".
"My god. This is bad, horrible, devastating news", Sen. One facet is to fund "neuroscience research aimed at understanding the brain's chemistry, structure, and circuits that led to violence and compassion".
After Newtown, the parents founded The Avielle Foundation, which supports research into the "neurological underpinnings of violence".
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