The gunman who opened fire at a Manhattan office building Monday, killing four people before taking his own life, legally purchased the rifle used in the attack, according to an attorney for the Las Vegas casino supervisor he bought it from.

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.