A gunman who killed four people at a Manhattan office building bought the rifle from his supervisor at a Las Vegas casino, authorities said.

Shane Tamura, 27, who fatally shot four people in the building that houses the National Football League's headquarters Monday, said in a suicide note that he had chronic traumatic encephalopathy, known at CTE,

Shane Tamura, the gunman who killed an NYPD officer and three civilians before taking his own life inside a Midtown Manhattan Park Avenue skyscraper, left a second suicide note behind in his Las Vegas home,