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.

The gunman suspected of targeting the National Football League headquarters in New York, killing four, was a former football player at two Southern California high schools.

The gunman suspected of targeting the National Football League headquarters in New York, killing four, was a former standout football player at two Southern California high schools.