A gunman who unleashed deadly chaos in a New York skyscraper on Monday evening, killing four people, left behind a disturbing note blaming the NFL for a brain condition he believed drove him to violence, Mayor Eric Adams revealed.

The shooter, 27-year-old Shane Tamura from Las Vegas, died by suicide after opening fire inside a building that houses the National Football League’s headquarters. But authorities say Tamura mistakenly exited the wrong elevator, directing his attack away from the league’s actual offices.

Tamura, who had never played professionally but participated in high school football, referenced chronic traumatic encephalopathy (CTE) in his note — a degenerative brain condition linked to repeated head injuries, often found in contact sport athletes. Adams said the gunman believed the NFL was responsible for his deteriorating mental health.

Among the victims was 36-year-old NYPD officer Didarul Islam, who was working a security post at the time of the assault. Three other individuals lost their lives and are awaiting formal identification. NFL Commissioner Roger Goodell confirmed that one league employee was also seriously wounded.

The attack appeared premeditated. Tamura reportedly drove cross-country from Las Vegas with an assault-style rifle. After firing in the building’s lobby, he took an elevator to the 33rd floor — mistakenly arriving at the offices of Rudin Management instead of the NFL’s.

“This is still an active investigation,” Adams noted, “but early findings suggest the NFL was his intended target.”