Months before police identified Luigi Mangione as the man they suspected shot a top health insurance company CEO and then seemingly vanished from midtown Manhattan, another disappearance worried his friends and family.

Mangione, the 26-year-old scion of a wealthy Baltimore family, valedictorian and Ivy League graduate, was active on social media for years, posting smiling photos from his travels, sharing his weight-lifting routine and discussing health problems he faced.

He publicly tracked nearly 300 books he had read or wanted to read, and even posted a positive review of the Unabomber Manifesto on a book website.

But then, over the summer, Mangione apparently stopped posting online, prompting worried messages from some of his friends.

“No one has heard from you in months and it seems your family is looking for you,” one user posted on X in October, tagging one of Mangione’s accounts. “I don’t know if you’re okay,” another posted.

As police now try to determine Mangione’s possible motive and actions leading up to last week’s shooting of UnitedHealthcare CEO Brian Thompson, those who know him are wondering how someone with a promising life could commit such a brazen crime could.

“I can’t make sense of it at all,” said RJ Martin, who lived with Mangione in a shared apartment in Hawaii a few years ago and remembered him as kind and considerate. “It’s unimaginable.”

A former colleague of Mangione’s, who worked with him as an advisor at a Stanford University summer program while he was a student, described him as outgoing and gregariously charming.

“I’m amazed,” the colleague said, asking not to be named because of the sensitivity of the message. “I never had the impression that he would destroy himself.”

Read more about how those who knew Mangione respond to the case.