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, 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,

Park Ave. gunman Shane Tamura bought the assault rifle he used to kill an NYPD cop and three civilians before taking his own life inside a Midtown Manhattan office building from a friend and