Four people were killed and a fifth was injured in a mass shooting at a Midtown Manhattan office building on Monday.One slain victim worked at Rudin Management -- which is located on the 33rd floor of 345 Park Avenue,

An NYPD officer, a Blackstone executive, a Rudin Management associate and a security guard were killed in the shooting at Manhattan's 345 Park Avenue.

Multiple casualties as gunman opened fire in the lobby of the midtown Manhattan building on Park Avenue that is home to the Blackstone investment firm and other corporations before moving to other floors.