A married father of two with a third child on the way, the 36-year-old was working a New York Police Department-approved private security detail, in uniform, when he and three other people were killed Monday at the Manhattan skyscraper that houses the NFL's headquarters and other corporate offices.

Four people were killed and a fifth was injured in a mass shooting at a Midtown Manhattan office building on Monday. The injured victim was an employee at the NFL, according to NFL Commissioner Roger Goodell. Here's what we know about the four people killed:

The 36-year-old, one of four who died in a Midtown Manhattan mass shooting, left behind a pregnant wife and two young boys.