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,

Police are retracing Tamura's movements from Nevada to New York after a Midtown Manhattan shooting that left four people dead and another wounded