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

The brain disease has most commonly been found in athletes in contact sports and others with a history of repeated brain trauma.

The gunman who opened fire in a Midtown Manhattan office building left a note that appeared to blame the National Football League for his brain injury, New York Mayor Eric Adams said on Tuesday.