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

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 (Reuters) -Bankers and traders returned to work on a somber Tuesday morning in Midtown Manhattan, New York's financial epicenter, one day after a shooting that killed four people, including a senior Blackstone executive.