Gunman who killed 4 in New York was trying to get to NFL offices and claimed to have CTE: Officials

Tamura, 27, shot several people in the skyscraper's lobby and another in a 33rd-floor office on Monday before he killed himself, authorities said. Among the victims were an off-duty New York City police officer and a security guard.

The attacker's grievances with the NFL emerged as police began piecing together the details of his life and the cross-country road trip that brought him to Manhattan.

Tamura, who played high school football in California a decade ago but never played in the NFL, had a history of mental illness, police said. In the three-page note found on his body, he accused the NFL of concealing the dangers to players' brains for profit. The degenerative brain disease has been linked to concussions and other repeated head trauma common in contact sports such as football, but it can only be diagnosed after someone has died.

In the note, Tamura repeatedly said he was sorry and asked that his brain be studied for CTE. It also referenced former NFL player Terry Long, who was diagnosed with CTE, and the manner in which Long killed himself in 2005.

The NFL long denied the link between football and CTE, but it acknowledged the connection in 2016 testimony before Congress and has paid more than $1.4 billion to retired players to settle concussion-related claims.

The shooting shakes Manhattan

NFL Commissioner Roger Goodell, who works out of the offices, called the shooting "an unspeakable act of violence in our building," saying he was deeply grateful to the law enforcement officers who responded and to the one who gave his life to protect others.

Goodell said in a memo to staff that a league employee was seriously injured in the attack and was hospitalized in stable condition.

The shooting happened along Park Avenue, one the nation's most recognized streets, and just blocks from Grand Central Terminal and Rockefeller Center. It's also less than a 15-minute walk from where UnitedHealthcare CEO Brian Thompson was shot and killed last December by a man who prosecutors say was angry over corporate greed.

The attack drew a response from the White House, with President Donald Trump posting on social media, "My heart is with the families of the four people who were killed, including the NYPD Officer, who made the ultimate sacrifice."

Video shows the gunman stroll into the building

Tamura, who worked security at the Horseshoe Las Vegas, drove across the country over the past few days and into New York City just before the attack, Police Commissioner Jessica Tisch said.

Detectives plan to question a man who supplied parts for the AR-15-style rifle Tamura used Monday, including the weapon's lower receiver, she said during a news conference.

Surveillance video showed Tamura getting out of a BMW early Monday evening and strolling across a plaza in a button-down shirt and jacket with the rifle at his side before he entered the building, which also has offices for the investment firm Blackstone and other companies. It was closed Tuesday except to investigators.

Once inside, he sprayed the lobby with gunfire, killing Didarul Islam, the off-duty police officer who was working a corporate security detail, and hitting a woman who tried to take cover, Tisch said. He then made his way to the elevator bank, shooting a guard at a security desk and another man in the lobby, she said.

"He appeared to have first walked past the officer and then he turned to his right, and saw him and discharged several rounds," Adams said in a TV interview.

Tamura took an elevator to the 33rd-floor offices of the company that owns the building, Rudin Management, and shot and killed someone there before fatally shooting himself, the commissioner said.

Blackstone confirmed that one of its employees, real estate executive Wesley LePatner, was among those killed. Security officer Aland Etienne also died, according to a labor union.

The off-duty officer was from Bangladesh

Islam, 36, had served as a police officer in New York City for three-and-a-half years and was an immigrant from Bangladesh, Tisch said. He was working a department-approved second job, in his New York Police Department uniform, providing security Monday at the Park Avenue building.

His body was draped in the NYPD flag as it was moved from the hospital to an ambulance, with fellow officers standing at attention.

Islam leaves behind a pregnant wife and two children. Friends and family stopped by their Bronx home on Tuesday to drop off food and pay their respects.

"He was a very friendly guy and a hardworking guy," said Tanjim Talukdar, who knew him best from Friday prayers. "Whenever I see him or he sees me, he says 'How are you, my brother?"