The New York Police Department says a gunman who ambushed two officers in their car told two passersby to "watch what I'm going to do."
Chief of Detectives Robert Boyce says 28-year-old Ismaaiyl Brinsley talked to people on the street just moments before the shooting and told them to follow him on the social media site Instagram.
Boyce said Brinsley had a criminal history with at least 19 arrests and his family told police he tried to hang himself last year.
Brinsley approached a parked squad car from behind on Saturday and opened fire, fatally striking two officers before killing himself. Hours earlier, he had shot and wounded his ex-girlfriend at her home outside Baltimore.
Boyce says Brinsley had ranted online about police and government and expressed despair about his own life.
A police officer lays flowers at a makeshift memorial at the scene where two police officers were shot dead in Brooklyn on Saturday. (Stephanie Keith/Reuters)
