Police have identified the man who they say entered a Midtown Manhattan office building wearing body armor and opened fire, killing four people with a high-powered rifle, as Shane Devon Tamura.

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, 27, who police said fatally shot four people Monday in the midtown skyscraper that houses the National Football League's headquarters, said in a suicide note that he believed he had chronic traumatic encephalopathy,