The man who unleashed chaos inside a Midtown Manhattan office tower on Monday afternoon has been identified as Shane Devon Tamura, a 27-year-old licensed private investigator from Las Vegas who once dreamed of a life in football.

Authorities say Tamura, who had a 'documented mental health history', arrived in Manhattan by car on Monday afternoon following a mammoth cross-country trip. 

The NYPD revealed on Monday night how Tamura had traveled through Colorado on July 26, through Nebraska on July 27 and through Columbia, New Jersey as recently as 4pm on Monday before arriving in Manhattan to carry out his deadly rampage.

When he arrived, he parked his black BMW around the corner from 345 Park Avenue in the heart of Midtown Manhattan before brazenly striding across a wide city plaza with his long-form M4 rifle in plain sight, by his side. 

Tamura had his concealed weapon permit issued by the Las Vegas Sheriff's Department on him as he walked straight into the building's lobby and opened fire.

Once in the lobby he sprayed it with gunfire, shooting an NYPD officer in the back and a security guard who took cover behind a desk, before heading to the elevator bank and headed up to the 33rd floor and the offices of Rudin Management who run the building and other offices across New York City.

The terrifying shooting spree killed four people with another person left fighting for their life. Police believe was the shooting was premeditated and likely suicidal.

'It appears that he knew it would be his last stand,' said CNN chief law enforcement analyst John Miller, a former NYPD deputy commissioner.

'He fully intended to shoot his way through the lobby and make his way to that target - whatever that might have been.'

The building, home to major corporate tenants including the NFL's headquarters, became the scene of a frantic lockdown as gunshots echoed through the corridors and heavily armed police teams swarmed the floors.  

Tamura, 27, was found with a letter on his body indicating he had grievances with the NFL and its handling of chronic traumatic encephalopathy (CTE). 

In the note he railed against the NFL and pleaded for his brain to be studied.

'Terry Long football gave me CTE and it caused me to drink a gallon of antifreeze,' Tamura wrote, according to CNN. 'You can’t go against the NFL, they’ll squash you.'

The shooter was referring to former Pittsburgh Steeler Terry Long, who committed suicide by drinking antifreeze in 2006 after suffering from CTE.

'Study my brain please I’m sorry Tell Rick I’m sorry for everything,' the note read.

While the league's offices are housed in the tower, sources confirmed Tamura did not enter the NFL floor.

Nevertheless, investigators are looking into into whether he was targeting the NFL offices based at that building. 

Officials say he had no criminal background but his past raises haunting questions.

Tamura grew up in Hawaii and was immersed in a life dominated by sports. 

He was a promising football player in junior varsity, obsessed with the game and once on a path that suggested a future defined by discipline and teamwork.

In a video posted online from the 2015 season, Tamura can be heard giving a post-game interview in which he spoke of his victory with the Granada Hills football team based in Southern California.

Shane was instrumental in his teams victory after scoring several touchdowns. 

'We were down 10-0, stayed disciplined and came together as a team. Couple of touchdowns,' he said on the day of his interview. 

His old high school friends in California said they were stunned to find out he was the shooter.

'You never would have thought violence was something you'd associate with him,' classmate Caleb Clarke told NBC.

'Everything he said was a joke.'

His former coach Walter Roby said Tamura was a talented football player and a 'quiet kid'.

'I'm just blown away right now,' he said. 

But in the years after he left the field, Tamura's life became murkier. 

He eventually relocated to Las Vegas, where he earned a private investigator's license and obtained a concealed carry permit to carry firearms, both legally granted through Nevada's Sheriff's Department.

The latter part of Tamura's life is largely invisible to the public. 

Investigators in both Nevada and New York are now urgently combing through his car, phone, and computer in search of answers to try and work out what stressors or perceived injustices led him to carry out Monday's deadly shooting. 

During a late night press conference NYPD Commissioner Jessica Tisch said the police found a rifle case with rounds, a loaded revolver, ammunition and magazines, as well as a backpack and medication prescribed to Tamura.

'Police want to know what brought him to that building, who or what the target was, and what the grievance or motive behind it might have been,' Miller explained. 

'These cases often involve people who experience a downfall and begin to blame others - bosses, institutions, society at large. 

'Then they decide to get even with everybody, even though in most cases, the problem is usually them,' Miller said.

Investigators are also poring over Tamura's social media footprint, hoping it might offer clues - manifestos, threats, cryptic posts, or grievances that might have foreshadowed his violent act. 

As of now, police have not said whether Tamura had any personal or professional connection to the building or its tenants, but they are leaving no stone unturned.

Authorities say there's no immediate evidence of any accomplices, but they are working methodically to verify that no other individual helped plan or facilitate his movements across state lines or into the high-security office tower.

Miller emphasized that shooters like Tamura often spiral quietly, building a world of resentment that no one sees until it erupts in tragedy.

'They blame their problems on other people and entities,' he said. 'Then they decide to get even - with the world, with everyone - even though the problem usually begins and ends with themselves.'

No motive has yet been officially released, but the scene suggests Tamura had a plan that ended with his own death.

The shooting caused widespread chaos in Midtown. Workers from nearby finance firms spilled into the streets, hands raised above their heads as NYPD officers locked down the building and initiated a floor-by-floor search.

Nearby worker Anna Smith, who had just stepped out to grab dinner, described the moment panic took over. “It was like a crowd panic,” she said. “People just started running. We had no idea what was going on.”

For roughly two hours, office workers were locked inside surrounding buildings as SWAT teams secured the area.

The city’s emergency management system issued alerts about road closures, subway disruptions, and traffic delays around Grand Central Terminal and St. Patrick’s Cathedral, both just blocks from the shooting scene.