The gunman who killed four people at an office building in New York City on Monday evening left his home in Las Vegas, Nevada late last week.

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.

Study my brain please,” read a note left by the gunman accused of killing four people in a building that houses NFL’s headquarters