By PHILIP MARCELO and ERIC TUCKER

NEW YORK (AP) — New York City Mayor Eric Adams said Tuesday that a gunman who killed four people at a Manhattan office building was trying to target the headquarters of the National Football League but took the wrong elevator.

Investigators believe Shane Tamura was trying to get to the NFL offices after shooting several people in the building’s lobby but accidentally entered the wrong set of elevator banks, Adams said in interviews on Tuesday.

Four people, including an off-duty New York City police officer, were killed. Police said Tamura had a history of mental illness, and a rambling note found on his body suggested he had a grievance against the NFL over an unsubstantiated claim that he suffered from chronic traumatic encephalopathy. He had played football in high school in California nearly two decades ago.

The note claimed he had been suffering from CTE — the degenerative brain disease that has been linked to concussions and other repeated head trauma common in contact sports like football — and said his brain should be studied after he died, a person familiar with the matter told The Associated Press.

It also specifically referenced the National Football League, the person said.

A motive has not been determined but investigators were looking into, based on the note, whether he might’ve specifically targeted the building because it is home to the NFL’s headquarters.

The shooting took place at a skyscraper that is home to the headquarters of both the NFL and Blackstone, one of the world’s largest investment firms, as well as other tenants.

A message sent to Blackstone employees, and obtained by The Associated Press, said a staff member at the private equity firm was killed in Monday’s shooting, but their identity was not immediately released.

Surveillance video showed the man exiting a double-parked BMW just before 6:30 p.m. carrying an M4 rifle, then marching across a public plaza into the building. Then, he started firing, Police Commissioner Jessica Tisch said, killing a police officer working a corporate security detail and then hitting a woman who tried to take cover as he sprayed the lobby with gunfire.

The man then made his way to the elevator bank and shot a guard at a security desk and shot another man in the lobby, the commissioner said.

The man took the elevator to the 33rd floor offices of the company that owned the building, Rudin Management, and shot and killed one person on that floor. The man then shot himself, the commissioner said. The building, 345 Park Avenue, also holds offices of the financial services firm KPMG.

The officer killed was Didarul Islam, 36, an immigrant from Bangladesh who had served as a police officer in New York City for 3 1/2 years, Tisch said at a news conference.

“He was doing the job that we asked him to do. He put himself in harm’s way. He made the ultimate sacrifice,” Tisch said. “He died as he lived. A hero.”