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.

The gunman who opened fire at a Manhattan office building Monday, killing four people before taking his own life, legally purchased the rifle used in the attack, according to an attorney for the Las Vegas casino supervisor he bought it from.