New York City was left reeling Monday evening after a deadly shooting at a prestigious office skyscraper on Park Avenue claimed five lives, including that of an NYPD officer, before the gunman turned the weapon on himself.

The tragic incident unfolded at 345 Park Avenue, home to the National Football League’s headquarters, when 27-year-old Shane Tamura opened fire inside the building, killing four people and injuring others before committing suicide on the 33rd floor.

Authorities have launched a full-scale investigation into the motive behind the mass shooting. However, early findings suggest a possible link to mental health struggles associated with sports-related brain trauma. According to The New York Post, a suicide note discovered near Tamura’s body referenced chronic traumatic encephalopathy (CTE), a degenerative brain condition often found in athletes with a history of repeated head injuries, and criticized the NFL’s handling of player safety.

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Tamura, a former high school football player who had more recently worked as a security guard in Las Vegas, reportedly wrote in his note that the sport “ruined his mind” and contributed to his declining mental health. The multi-page letter also reportedly described feelings of paranoia, depression, and disorientation, which he linked directly to his past football experience.

Law enforcement sources, who spoke on condition of anonymity, said the letter could provide a critical window into Tamura’s troubled state of mind leading up to the attack. No known connection between Tamura and the victims has yet been confirmed.

The NYPD, FBI, and mental health experts are now collaborating to examine the full extent of Tamura’s medical history and potential signs of untreated neurological issues. The case has reignited debate around the long-term risks of contact sports and raised pressing questions about security protocols in high-profile office buildings.

The names of the victims have not yet been released as authorities notify families.

City officials have condemned the attack as a “shocking act of violence” and have vowed to support the victims’ families while strengthening security measures at public and private institutions.

More updates to follow as the investigation continues.