The contents of the handwritten “suicide note” left by the gunman before he killed four people in a New York office tower have now been revealed.

On Monday evening (July 28), Shane Tamura, 27, opened fire at around 6:30PM in the lobby of 345 Park Avenue, a luxury skyscraper that houses the NFL’s headquarters.

He fatally shot Officer Didarul Islam, 36, who was working a security detail, and then fired at others in the lobby, injuring several people, including a fifth victim – believed to be an NFL employee – who remains in critical condition.

The shooter then proceeded to the 33rd floor, where he killed another person and then fatally shot himself in the chest.

A multi-page note was discovered after Tamura’s death, and authorities revealed that it contained long-harbored grievances against the National Football League (NFL) and included explicit references to CTE, a brain disease linked to repeated head trauma.

“Terry Long football gave me CTE, and it caused me to drink a gallon of antifreeze,” the letter read, according to sources familiar with the investigation, per The Mirror. “You can’t go against the NFL, they’ll squash you.”

He also added: “CTE chronic traumatic encephalopathy. Continues…