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 alleged gunman was identified as 27-year-old Shane Tamura, of Nevada. Police said the motive for the shooting remains under investigation and investigators are working to understand why the suspect targeted the commercial building.