The report points out the warning signs, which include bullying and grievances with classmates, a clear interest in hate groups or previous attacks and behavior that concerned family and friends.
"There was nothing in this report that surprised me," says Nicole Hockley, the co-founder of Sandy Hook Promise.
Hockley lost her son Dylan during the Sandy Hook school shooting. She says Sandy Hook Promise teaches kids across the country about the warning signs and how to speak up.
"There's still this fear of being seen as a 'snitch' or, you know, someone who's telling on someone else," she says.
The Secret Service found another common thread - easy access to guns.
"We need comprehensive policies," says Po Murray, of the Newtown Action Alliance.
She says Connecticut's Red Flag Law has saved lives.
In 2019, Norwalk police used the Red Flag Law to arrest Brandon Wagshol - seizing an arsenal of weapons.
His family tipped off police.
"When arrested, Brandon stated it was his intention to build a high-capacity firearm," says Wagshol's mother, Joanne Kirson.
News 12's John Craven is taking a deep dive into the new report this weekend on Connecticut Power and Politics.