New York shooting: gunman said in note that playing football gave him CTE

Detectives still trying to determine motive in attack that killed four in Manhattan on Monday

The gunman identified in the mass shooting in New York on Monday that killed four victims - including a police officer - was a former high school football player who left a note complaining that the sport had given him the brain injury known as CTE.

Detectives are still trying to determine the motive behind 27-year-old Shane Devon Tamura's shooting spree in 345 Park Avenue in Manhattan on Monday. It ranks as the deadliest firearms attack in New York City in a quarter of a century.