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.

The man who stormed a Manhattan office tower with a gun, killing four people before killing himself, worked in the surveillance department of a Las Vegas casino, part of an industry built on watching for threats before they unfold.

New York City investigators believe a co-worker of the Las Vegas man who killed four, including a police officer, provided a component of the deadly weapon, the 8 News Now Investigators have learned.