No motive has been announced. A suicide note was found expressing grievances with the NFL and saying Tamura suffered from CTE, a source said. Follow for live updates.

Investigators are examining why the gunman who killed four people before taking his own life at a New York City office tower targeted the National Football League and whether he suffered from a brain disease.

A man stalked through a Manhattan office tower firing a rifle Monday, killing four people, including a New York City police officer, and wounding a fifth before taking his own life, officials said. The shooting took place at a skyscraper that is home to the headquarters of both the NFL and Blackstone,