The gunman who killed an NYPD officer and three other people in a Midtown building on Monday evening was carrying a note that offered clues into his possible motive, sources told The Post.

A lone gunman opened fire at a Manhattan office tower that houses the NFL and Blackstone, killing four people.

Shane Tamura, 27, killed an NYPD officer and three other people on Monday evening when he stormed the Midtown skyscraper that’s home to the football league’s headquarters.

Tamura, 27, said in the note, which he had on him when he died and is a few pages long, that he wants his brain to be studied, the sources said.

The 27-year-old man who shot and killed four people at a Midtown office building on Monday carried a note in his pocket claiming he suffered from CTE, asked that his brain be studied and made references to the NFL.

Shane Devon Tamura, identified as the shooter at NFL HQ, left a note stating he suffered from CTE and wished for his brain to be examined.

Follow Daily Mail's live blog for the latest updates on the Midtown Manhattan shooting as the investigation continues.

Shane Tamura from Las Vegas caused a deadly shooting in Manhattan. The incident occurred at 345 Park Avenue. Tamura killed four people, including offi