A New York police officer, a “beloved” security guard, a young Cornell graduate and a senior executive with investment firm Blackstone were killed Monday when a lone gunman stormed a sprawling office tower in Midtown Manhattan and opened fire.

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.

Four people were killed and a fifth was injured in a mass shooting at a Midtown Manhattan office building on Monday. Among those killed was an officer who was a dad of two with a third on the way.