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 New York City office building where a gunman fatally shot four people and himself reopened Monday, one week after the deadly rampage.Workers returned to 345 Park Ave., in Midtown Manhattan under the watchful eyes of NYPD officers and a surplus of additional security following the mass shooting.

On Monday, workers trickled back into 345 Park Avenue in Midtown Manhattan, a skyscraper home to high-profile tenants including the NFL and asset management firm Blackstone. New York City police officers and a police dog were seen guarding the building,