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.

Didarul Islam, 36, was a father of two, with a third on the way, and was working a second job as a security guard at the building where shots rang out.

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,