According to NYPD Chief of Detectives Robert Boyce, cop killer Ismaaiyl Brinsley spoke with two passersby "just prior" to Saturday's shooting in Brooklyn, asking them for their gang affiliation and to follow him on Instagram before saying, "Watch what I'm going to do."

In a press conference on Sunday, Boyce revealed this and other details about the shooter discovered during the ongoing investigation, including that Brinsley's mother believed her son to have an undiagnosed mental illness and that he had reportedly attempted suicide as recently as a year ago.

Boyce said that Brinsley's social media posts expressed anger against the government, the police and himself. "Right now we have no gang affiliation, at all, attributed to this man," said Boyce, adding,"he has no religious statements that we found on Instagram at all, none whatsoever."

[Image via Instagram]