The man who opened fire in a Midtown Manhattan office building, killing four people and wounding a fifth, appeared to be targeting the NFL headquarters and had a note claiming he suffered from CTE, police sources told ABC News.

Multiple casualties as gunman opened fire in the lobby of the midtown Manhattan building on Park Avenue that is home to the Blackstone investment firm and other corporations before moving to other floors.

The shooter behind a deadly rampage inside an office building in Midtown Manhattan on Monday evening was apparently targeting NFL offices there, New York City Mayor Eric Adams said Tuesday morning. Adams said investigators recovered a three-page rambling note from gunman Shane Tamura's wallet in which he referenced the brain disease CTE.