Police say a gunman who killed four people in a Manhattan skyscraper before taking his own life claimed to have a brain disease linked to contact sports and was trying to target the National Football

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.

A shooting Monday at an office building in New York City that is home to the Blackstone investment firm and the NFL left four people dead, including an NYPD officer.

NYC shooting victims Didarul Islam, Wesley LePatner, Aland Etienne, and Julia Hyman were killed by a gunman inside Manhattan's 345 Park Ave.

A New York City police officer and an executive at an investment firm are among the four people killed by a gunman at a Manhattan office tower

Businesses across the U.S. are reevaluating security after a shooting at a New York City office building raised concerns about workplace safety.