Suspect Shane Tamura died by suicide after the Monday mass shooting at 345 Park Avenue, which is home to NFL headquarters. One page of the note found in Tamura's pocket accused the NFL of concealing the dangers to players’ brains to maximize profits, sources said.

Shane Tamura, the Park Ave. gunman who killed an NYPD officer and three others before taking his own life, left behind a suicide note saying he suffered from CTE, a brain injury often linked to playing football, and was targeting the NFL — but took the wrong elevator, officials said Tuesday.