NEW YORK — The man who killed four people in a rampage with a rifle through a Midtown Manhattan office building was carrying a note that appeared to blame the National Football League for his degenerative brain disease, New York Mayor Eric Adams said on Tuesday.

Police have identified the shooter as Shane Tamura, a 27-year-old Las Vegas resident with a history of mental illness struggles, who ended the Monday evening massacre by shooting himself in the chest on the 33rd floor of a Park Avenue office tower.

The NFL has its headquarters in the skyscraper, but Tamura apparently entered the wrong elevator bank and ended up in the offices of Rudin Management, a real estate company, where he shot employees, the mayor said.

“The note alluded to that he felt he had CTE, a known brain injury for those who participate in contact sports,” Adams told CBS News. “He appeared to have blamed the NFL for his injury.”

Chronic traumatic encephalopathy is a serious brain disease with no known treatment that can be caused by repeated bangs to the head from contact sports. It has been linked to aggression and dementia, and the NFL has paid an estimated $1 billion to settle concussion-related lawsuits with thousands of retired players after the deaths of several high-profile players.

Tamura was never an NFL player, but online records show he played in high school. The note found in his wallet said his football career was cut short by his brain injury, Bloomberg News reported.

Blackstone also has its headquarters in the tower, and one of the private equity firm’s executives was among those Tamura killed, while others were injured and taken to hospital.

Tamura also killed a New York Police Department officer, Didarul Islam, 36, who came from Bangladesh and had been on the force three years, the mayor said.

An NFL employee was also injured in the shooting and was in stable condition at a hospital, the Journal reported, citing a memo sent by NFL commissioner Roger Goodell to league staff.

Goodell wrote there would be “increased security presence” at the league’s offices “in the days and weeks to come,” ESPN reported.

Authorities offered few details about the three other victims besides the police officer – two men and a woman. A third man was gravely wounded by the gunfire and was “fighting for his life” in a nearby hospital, the mayor said.

History of Mental Illness

Tamura appeared to have driven to New York City from Las Vegas over three days and to have acted alone, New York Police Commissioner Jessica Tisch told reporters on Monday night.

He entered the skyscraper’s lobby, turned to his right and immediately shot the NYPD officer, who was assigned to the building’s security detail, Tisch said. She said Tamura used an M4 Carbine, a semi-automatic rifle popular with civilian U.S. gun enthusiasts modeled on a fully automatic rifle used in the U.S. military.

He then shot a woman and two men in the lobby but inexplicably allowed another woman to pass him unharmed before he took the elevator to the 33rd-floor offices of Rudin Management. There he fatally shot his final victim before taking his own life, Tisch said.

A widely circulated photo showed the permit issued to Tamura by the Las Vegas Metropolitan Police Department allowing him to legally carry a concealed firearm.

A loaded revolver was later recovered from the black BMW vehicle Tamura had left double-parked outside the office tower, along with a backpack and prescription medications, Tisch said.

—

(Reporting by Lananh Nguyen, Michelle Nichols and Daniel Fastenberg in New York, Doina Chiacu and Kanishka Singh in Washington; Additional reporting by Brad Brooks, Brendan O’Brien and Ismail Shakil; Writing by Steve Gorman and Jonathan Allen; Editing by Dan Burns, Sandra Maler, Frank McGurty, Michael Perry and Nick Zieminski)