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

New York City police detectives searched a studio apartment in Las Vegas that belonged to the suspected gunman in Monday's mass shooting at a Midtown Manhattan.

Shane Tamura, 27, is the suspect alleged to have shot and killed four victims while wounding an NFL employee. Tamura then fatally wounded himself. Further investigation into the shooting revealed that Tamura was targeting the NFL's offices, but "appeared to have gone to the wrong floor" in the 44-story skyscraper.