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

Authorities say Tamura arrived in Manhattan by car on Monday and walked into 345 Park Avenue in the heart of Midtown Manhattan with a concealed weapon permit issued by the Las Vegas Sheriff's Department.

What followed was a terrifying and targeted shooting spree that police believe 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.

While the league's offices are housed in the tower, sources confirmed Tamura was not on the NFL floor and that no known connection has yet been established between the shooter and the sports organization.

The man who unleashed chaos inside a Midtown Manhattan office tower on Monday has been identified as Shane Tamura, 27

Photos posted online showed the gunman wearing a sport coat and button-down shirt while carrying the large rifle near a midtown Manhattan office building

Still, his past raises haunting questions.

Tamura grew up in Hawaii, where he attended high school 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.

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 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 the deadly shooting.

'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.

New York State Police troopers were seen responding to the scene at 365 Park Avenue

'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.

The New York Police Department told the public to avoid the area of East 52 Street between Park Avenue and Lexington Avenue

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.

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