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.

The gunman in the deadly Midtown Manhattan shooting, Shane Tamura, wrote about the brain disease CTE in a note obtained by investigators.

The gunman, who said in a note he believed he had CTE, targeted skyscraper that houses the NFL's headquarters.