What we know about the NYC shooting and suspect Shane Devon Temura

A gunman opened fire inside a high-rise corporate building in the heart of Manhattan on Monday evening, killing a New York City police officer, a Blackstone executive and two other people, officials said.

The suspected shooter acted alone and died from a self-inflicted gunshot wound, law enforcement officials told NBC News.

The deadly gunfire, which was first reported about 6:30 p.m., was treated as an active shooting, prompting warnings and office evacuations, with lines of people seen leaving the building with their hands above their heads.

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The gunman’s motive has not been disclosed. Officials familiar with the investigation told NBC News, however, that the suspect left a note that mentions a possible cause of his mental illness.

Investigators are looking into whether that is a reason he targeted the Park Avenue building, which houses the NFL’s headquarters, the officials said.

Here’s what we know so far:

The victims

A 36-year-old police officer who was expecting his third child was killed, officials said.

Didarul Islam, who emigrated to the United States from Bangladesh, had been with the NYPD for 3½ years, Mayor Eric Adams said. He was assigned to the 47th Precinct in the Bronx.

“He was doing what he does best and all members of the police department carry out,” Adams said. “He was saving lives. He was protecting New Yorkers.”

Islam was the father of two young boys and was expecting a third child with wife, Police Commissioner Jessica Tisch said.

“He put himself in harm’s way. He made the ultimate sacrifice — shot in cold blood, wearing a uniform that stood for the promise that he made to this city,” Tisch said, calling him a hero.

Three civilians also died, including Blackstone executive Wesley LePatner, according to the investment firm.

LePatner was the global head of “Core+ Real Estate” and CEO of one of the largest funds owned by Blackstone, the Blackstone Real Estate Income Trust, or BREIT, according to the investment firm’s website. She joined the firm in 2014 after spending more than a decade working at Goldman Sachs, where she began her career.

“Words cannot express the devastation we feel.” Blackstone said in a statement.

The firm added that “Wesley was a beloved member of the Blackstone family and will be sorely missed.”

“She was brilliant, passionate, warm, generous, and deeply respected within our firm and beyond,” the firm said. “She embodied the best of Blackstone.”

Authorities have not released the names of the two other people killed in the shooting. A fifth person was critically wounded.

Early Tuesday, the NFL, which has its headquarters in the office tower, said one of the league’s employees had been wounded in the attack.

NFL Commissioner Roger Goodell said in a statement to employees that the wounded worker was hospitalized in stable condition.

“We are deeply grateful to the law enforcement officers who responded to this threat quickly and decisively and to Officer Islam, who gave his life to protect others,” Goodell said.

The gunman

Law enforcement officials said the violence was carried out by a lone gunman, who died from a self-inflicted gunshot wound.

The suspect has been identified as Shane Devon Tamura, 27, of Las Vegas, according to four senior law enforcement officials.

In a photo three law enforcement officials shared with NBC News, the gunman is seen walking into the midtown Manhattan building wearing dark clothes and sunglasses and carrying what appears to be a large firearm.

In addition to the weapon and ammo, a cellphone was found at the scene and attempts will be made to see what it contains, the officials said.

A motive has not been determined but investigators are looking into a note left by the suspect, officials said.

Two officials familiar with the matter said that in the note the suspect wonders about “CTE” as being a possible cause of his mental illness.

Caleb Clarke, a former classmate and high school football teammate, said Tamura “was the biggest goofball in the world, just a ton of energy, class clown.” The two played together in California until Tamura transferred from a Santa Clarita high school to Grenada Hills High School in 2015, just before their senior year.

Clarke said that in recent years, he and Tamura kept up only through social media, where Tamura shared that he had been working at a casino in Las Vegas.

Clarke didn’t recall Tamura ever being a troublemaker in school. “You never would have thought violence was something you’d associate with him,” Clarke said. “You know, he could make a joke about people, but that’s just typical. Shane was a jokester. Everything he said was a joke. He had a ton of energy.”

He added that it seemed as if Tamura was destined for greatness as an athlete. “I feel like it was definitely on the table for him,” Clarke said. “I don’t think he walked around to be like, ‘Oh, I’ll have NFL games one day.’ I think it was more of everybody just telling him how great he was … how special he was.”

The building

Midtown Manhattan’s 345 Park Ave. is the headquarters of the investment firm Blackstone.

The building also hosts the headquarters of the NFL and a Bank of America branch, as well as offices belonging to KPMG.

Blackstone, Bank of America and the building’s owner, Rudin Management, did not immediately respond to requests for comment.

In a statement, KPMG said its thoughts were with victims and their families.

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