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 — who fatally shot four people at a Midtown East office building — said in a suicide note he believed he suffered from CTE and requested his brain be studied.