A gunman armed with an assault-style rifle killed four people inside a Manhattan skyscraper that houses the headquarters of the NFL and offices of several major financial firms and then shot himself dead,

A suspect had opened fire inside a midtown office tower when the 36-year-old NYPD officer, Didarul Islam, was working on a paid security detail in the building.

A lone gunman walked into a midtown Manhattan office building Monday and opened fire, killing four people, including an NYPD officer, before turning the gun on himself.