NYC mass shooter Shane Tamura had a note blaming the NFL for his CTE, despite never playing professional football

The crazed gunman who killed an NYPD officer and three other people in a Midtown skyscraper on Monday evening was carrying a note in his pocket that expressed grievances with the NFL and claimed he suffered from CTE – a brain injury linked to head trauma, sources told The Post.

Shane Tamura, 27, cited the NFL in the writings, which were found after he fatally shot himself in the chest on the 33rd floor of 345 Park Ave. – a swanky skyscraper that houses the football league’s headquarters.

The mentally ill shooter wanted to shoot up the NFL HQ — but “mistakenly went up the wrong elevator banks” and ended up on a higher floor, Mayor Eric Adams confirmed Tuesday.

In the ramblings, which was several pages long, Tamura blamed football for his apparent struggle with the neurodegenerative disease chronic traumatic encephalopathy (CTE) and pleaded for his brain to be studied in the wake of the massacre, law enforcement sources said. 

He wrote addressing Terry Long, the former Pittsburgh Steelers player who was diagnosed with CTE after downing antifreeze to kill himself 20 years ago.

“Terry Long, football gave me CTE and it caused me to drink a gallon of antifreeze,” the note stated, according to sources.

“You can’t go against the NFL, they’ll squash you.”

“Please study brain for CTE. I’m sorry. The league knowingly concealed the dangers to our brains to maximize profits,” he wrote. “They failed us.”

The NFL has offices on floors five through eight of the Park Avenue high-rise, and one of its employees was among those shot, though not fatally..

Mayor Adams confirmed early Tuesday that Tamura’s note “alluded to having CTE from playing NFL” — even though “he never played in the NFL.”

“It appears as tho he was going after the employees of the NFL,” the mayor confirmed on Fox 5.

“We’re still going through the suicide note to zero on in the exact reason but at this time it appears as if it’s something attached to his belief he experienced CTE from the NFL.”

Shortly after the shooting, NYPD Commissioner Jessica Tisch directly called executives at Blackstone – another notable tenant in the skyscraper – to inform them that they weren’t the intended targets, sources said.

Tamura, who lived in Las Vegas and had a known mental health history there, initially opened fire in the building’s lobby before taking the elevator up to the 33rd floor where he turned the gun on himself.

He also shot a fifth victim in the lobby of the building who survived the attack, police said.

The surviving victim appears to an NFL employee, as the league’s commissioner, Roger Goodell, told staffers in a letter that one of their own had been “seriously injured” in the shooting.

Meanwhile, NYPD Commissioner Jessica Tisch had earlier revealed the maniac gunman, who lived in Las Vegas, had a known mental health history.

Tamura, who worked a security guard at a Las Vegas casino, never played professional football.

But he did play in high school in California, when he was a described as a standout football player.

“It looked like the sky was the limit, and then it wasn’t anymore,” former classmate Caleb Clarke told NBC News. Ahead of his senior year, his coach told the Los Angeles Times that he expected “big things” from the running back and other star players on the team.