The gunman who killed four people in a Midtown Manhattan skyscraper accused the National Football League in a suicide note of concealing the dangers of the sport on players’ brains, according to a New York Police Department official.

Shane Tamura, 27 years old, used an AR-15-style rifle to kill an NYPD police officer in the lobby of the building, as well as a security guard, an executive of financial firm Blackstone and a real-estate firm employee before shooting himself in the chest, police said.

Investigators recovered three pieces of paper from Tamura’s wallet that included a request that his brain be studied for chronic traumatic encephalopathy, the official said. The disease is associated with head injuries that can be diagnosed conclusively after an autopsy.

A CCTV image, which the WSJ has verified with an NYPD spokesman, showed the shooter entering the Midtown Manhattan building with a rifle.

“The league knowingly concealed the dangers to our brains to maximize profits,” the note said on one page, according to the official. “They failed us.”

A spokesperson for the NFL referred a request for comment to the NYPD.

Shane Tamura

The building where the shooting took place—345 Park Avenue—is in the heart of Midtown Manhattan and has offices for the NFL, Blackstone, accounting firm KPMG and real-estate management firm Rudin Management.

The Rudin family, one of New York’s real estate dynasties, owns the building.

Detectives were headed to Las Vegas, New York City Mayor Eric Adams said Tuesday.

“We are still unraveling this terrible shooting in the city,” Adams said in an interview with CNN.

Detectives will question an associate of Tamura’s who bought and gave him the rifle’s lower receiver, which houses the firing mechanism, NYPD Commissioner Jessica Tisch said Tuesday in a video addressing department officers.

Police are also searching Tamura’s car and two phones left at the scene. He legally purchased a revolver on June 12, using a Nevada concealed carry permit, Tisch said.

The gunman came to New York City Monday afternoon after driving his BMW across the country, passing through Colorado on Saturday and Nebraska and Iowa on Sunday, police said.

Tamura worked in the surveillance department at casino hotel Horseshoe Las Vegas but didn’t show up on Sunday, according to Tisch. Once in New York City, Tamura double-parked on Park Avenue at around 6:30 p.m., and walked into the building openly holding the rifle, authorities said.

Tamura first shot and killed NYPD Officer Didarul Islam, 36, an immigrant from Bangladesh who is a married father of two children, police said.

Tamura shot up the lobby, killing Wesley LePatner, CEO of Blackstone’s real-estate megafund, who was taking cover behind a pillar, and security guard Aland Etienne, according to Blackstone and the SEIU union.

The gunman then rode the elevator up to the 33rd-floor office of Rudin Management, where he killed Julia Hyman, a 27-year-old Rudin employee, before shooting himself in the chest. Hyman started working at Rudin less than a year ago on the firm’s capital markets team.

Tamura appeared to have been headed to the NFL offices but went to the wrong elevator bank and ended up on the floor of Rudin Management by mistake, Adams said.

Didarul Islam, the NYPD officer killed in the shooting. was assigned to the 47th Precinct the Bronx.

Memorial flowers outside the Blackstone headquarters.

Inside the shooter’s car, police found a rifle case with rounds, a loaded revolver, ammunition and magazines, and medication prescribed to Tamura.

The suicide note contained a reference to Terry Long, a former NFL player in the late 1980s and early 90s who died in 2005 after consuming antifreeze. His death was ruled a suicide and an autopsy revealed that Long had CTE. “You can’t go against the NFL, they’ll squash you,” Tamura wrote, according to an official.

On another page, the note said, “Study my brain please. I’m sorry. Tell Rick I’m sorry for everything.” It is unclear who Rick refers to.

Write to James Fanelli at [email protected], Joseph De Avila at [email protected] and Jack Morphet at [email protected]