A shooting Monday at an office building in New York City that is home to the Blackstone investment firm and the NFL left four people dead, including an NYPD officer.

The NFL season kicked off at the annual Hall of Fame game with a moment of silence for the four people killed earlier this week by a shooter who was targeting league headquarters in New York. The gunman also wounded a league employee in the shooting Monday night.

A fifth shooting victim -- an NFL employee, according to Commissioner Roger Goodell -- was injured and taken to the hospital in critical condition, officials said. That victim was listed in stable condition on Tuesday morning, according to a source familiar with the individual's status.