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.

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,

The funeral will be held Thursday for the police officer who was one of four people killed in Monday's mass shooting at a Midtown Manhattan office building.