Officer Didarul Islam, 36, who was guarding the building on a paid security job when he was killed, had served as a police officer in New York City for over three years. He was an immigrant from Bangladesh and was working a department-approved building security job when he was shot.

Authorities confiscated several items from a Las Vegas apartment tied to a gunman who used an AR-15-style rifle to kill four people in Manhattan, according to records made public Friday.

A gunman who killed four people at a Manhattan office building bought the rifle from his supervisor at a Las Vegas casino, authorities said.