The shooter who killed four people on Monday evening at a Midtown Manhattan office building left a suicide note in which he appeared to be targeting the National Football League at its headquarters.

The suicide note suggested he believed he had chronic traumatic encephalopathy, a brain disease associated with head injuries, New York City Mayor Eric Adams said Tuesday. The shooter, who has a history of mental illness, blamed the NFL for his condition, Adams said.

“It appears as though he was going after the employees at the NFL,” Adams said in a television interview Tuesday with a local Fox affiliate.

NYPD Commissioner Jessica Tisch said the gunman was 27-year-old Shane Tamura from Las Vegas. He carried an M4 rifle, she said.

Among the four slain victims were an executive from financial firm Blackstone and a New York City police officer.

The gunman shot a fifth person, an NFL employee who was in critical condition, before turning the gun on himself.

NYPD officers on Tuesday worked near the scene of a deadly mass shooting in Midtown Manhattan.

The office tower where the shooting unfolded is an iconic New York address, 345 Park Avenue, in the heart of the city. The area is packed with workers from the worlds of high finance, law and accounting. Blackstone, a buyout firm that has been a Wall Street power player for decades, is among the building’s major tenants. The National Football League and accounting firm KPMG also have offices there.

Tamura, who the police said has a documented history of mental illness, arrived in New York City on Monday afternoon after driving his black BMW across the country, passing through Colorado on Saturday and Nebraska and Iowa on Sunday. He double-parked on Park Avenue during the evening rush, around 6:30 p.m., got out with the rifle in his right hand and started shooting as soon as he was inside the building lobby, the police said.

Tamura first shot and killed NYPD Officer Didarul Islam, 36, an immigrant from Bangladesh who is a married father of two children, Tisch said. The officer’s wife is pregnant with their third child.

Tamura sprayed the lobby with gunfire, shooting a woman taking cover behind a pillar and a security guard hiding behind a desk, according to the police.

Wesley LePatner, a senior managing director at Blackstone, was killed in the attack, the company said Tuesday.

“Words cannot express the devastation we feel,” Blackstone said in a statement. “Wesley was a beloved member of the Blackstone family and will be sorely missed.”

The gunman then rode the elevator up to the 33rd-floor office of real-estate management firm Rudin Management, where he killed another person before shooting himself in the chest. The Rudin family, one of New York’s real estate dynasties, owns the building.

“Our thoughts and prayers are with those injured and lost last night, including our cherished Rudin colleague, a brave New York City police officer, a beloved lobby security guard and an employee at a tenant firm,” the Rudin family said in a statement.

The office building was closed Tuesday as officials continued their investigations.

Security officer Aland Etienne was also killed in the attack, his union said. Manny Pastreich, president of 32BJ SEIU, described Etienne as a dedicated worker who took his job very seriously.

“Aland Etienne is a New York hero,” Pastreich said in a statement released by the union. “We will remember him as such.”

The shooter 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 in his interview.

An ambulance carrying the body of Didarul Islam exits NewYork-Presbyterian/Weill Cornell Medical Hospital early Tuesday.

Blackstone employees shared messages over email and Microsoft Teams that there was a shooter in the lobby and warned each other not to go downstairs, an employee said. Some barricaded themselves in offices and bathrooms.

Police Officer Didarul Islam

“Our hearts go out to the victims of this horrific act and their families. We are incredibly grateful for the bravery of building security and law enforcement,” said Russ Grote, a KPMG US spokesman.

The shooting happened five blocks from where UnitedHealthcare executive Brian Thompson was shot dead late last year, with Luigi Mangione charged with murder.

One of the people injured Monday was an NFL employee, according to a letter commissioner Roger Goodell sent to league staff. Goodell wrote that the employee was seriously injured and at a hospital in a stable condition. Goodell also directed the league’s New York-based employees to work remotely Tuesday, adding that it is understandable if they prefer to take the day off.

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

Tamura faced a misdemeanor trespassing charge in Nevada in 2023, court documents showed, and once held a private investigator’s license.

Write to Jack Morphet at [email protected], Miriam Gottfried at [email protected] and James Fanelli at [email protected]