Nevada man recently traveled to New York City, entered a Manhattan building wearing body armor, carrying an M4 rifle, and fatally shot four people Monday evening, including a New York Police Department officer and injured another, before killing himself. 

The act is one of the deadliest mass shootings the city has seen in 25 years. Investigators are probing the Midtown attack, the gunman and a possible motive.

Here’s everything to know about the deadly shooting, including details about the gunman, when and where the incident occurred, the victims, and how the suspect’s mental health played a central role.

Who is Shane Tamura?

The shooting suspect, Shane Tamura, 27, of Las Vegas, was captured on surveillance footage leaving a double-parked black BMW and walking into an office building at 345 Park Ave. at East 52nd Street just before 6:30 p.m. Monday, NBC News reported.

The building is home to several global firms, including Blackstone, the National Football League, Rudin Management and KPMG.

He sprayed gunfire in the lobby and again on the 33rd floor, striking multiple people on both levels before killing himself, New York Police Commissioner Jessica Tisch said at a Monday evening news conference.

“According to our law enforcement partners in Las Vegas, Mr. Tamura has a documented mental health history,” Tisch said. “His motives are still under investigation.”

What mental health issues did Shane Tamura have, and what did he say about the NFL?

Tamura also had a note in his pocket, claiming he suffered from chronic traumatic encephalopathy, a brain disease linked to head trauma from contact sports like football and other areas, where repetitive head injuries can happen, according to Indiana University School of Medicine.

“You can’t go against the NFL, they’ll squash you,” Tamura wrote in the three-page note investigators found at the shooting, according to a source familiar with the matter.

In the third page, Tamura said, “Study my brain please. I’m sorry,” sources said, per ABC 7 New York.

Tamura played football in high school. Those who knew him were shocked to hear that he was the suspected gunman in the mass shooting.

“He was a great teammate. He was a great guy in general. He didn’t cause any problems actually at all in the locker room or on the field,” one of Tamura’s former teammates told KABC Los Angeles. “He was just a guy who really enjoyed the sport, not problematic at all so when I found out the news, I was really shocked, I really couldn’t believe it.”

Source: Who Was Shane Tamura, The Midtown Manhattan Shooting Suspect, And Why Did He Target The NFL?