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:

NEW YORK (AP) — A man stalked through a Manhattan office tower firing a rifle Monday, killing four people, including a New York City police officer, and wounding a fifth before taking his own life, officials said.

A gunman opened fire inside the Manhattan skyscraper that is the headquarters of private-equity firm Blackstone and the NFL, killing four people, including a police officer, before fatally shooting himself on Monday evening, authorities said. Another person was in critical condition, and others suffered less serious injuries.