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.

Tamura's supervisor at the Horseshoe Las Vegas legally bought the AR-15-style rifle he sold to Tamura for $1,400, the New York Police Department said Wednesday.

The attorney for the man who sold what would become the deadly weapon in a mass shooting in New York City earlier this week said his client legally sold his co-worker the gun.