Players and coaches around the NFL reacted with shock and sadness Tuesday after a gunman killed four people at the New York office building housing the league's headquarters.

Read the note NFL Commissioner Roger Goodell sent to staff. National Football League Commissioner Roger Goodell sent a note to staff encouraging them to work remotely or take the day off following Monday's fatal shooting at its New York City office building.

Police say a gunman who killed four people in a Manhattan skyscraper before taking his own life claimed to have a brain disease linked to contact sports and was trying to target the National Football