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, who fatally shot four people in the building that houses the National Football League's headquarters Monday, said in a suicide note that he had chronic traumatic encephalopathy, known at CTE,

Officials said the gunman fatally shot himself after his attack, which set off a chaotic scene that rippled out into the heart of Manhattan during rush hour.