New details have emerged in the Manhattan office shooting, with investigators discovering Shane Tamura’s suicide note, suggesting he may have a grudge against the NFL over chronic traumatic encephalopathy (CTE).According to CNN, the 27-year-old gunman who killed himself following the attack on July 28, 2025, left behind a three-page letter mentioning former Pittsburgh Steelers player Terry Long, who also had CTE and killed himself by drinking antifreeze in 2005.The note, found in Shane Tamura’s back pocket, contained parallels to Long’s death."Terry Long, football gave me CTE and it caused me to drink a gallon of antifreeze," Tamura wrote, sources told CNN. "You can’t go against the NFL, they’ll squash you."The mention of Long, a former offensive lineman who was diagnosed with CTE, is intended to indicate that Tamura thought he, too, had the degenerative brain disease associated with repeated head trauma. In the note, he begged: "Study my brain, please I’m sorry Tell Rick I’m sorry for everything.” The man referred to as "Rick" has yet to be publicly identified by authorities.New York City Mayor Eric Adams and law enforcement officials are investigating whether Shane Tamura intended to attack the NFL’s headquarters but took the wrong elevator. The shooting took place in 345 Park Avenue, a commercial tower that is home to the NFL’s offices, as well as other major companies.During a July 29 episode of The Megyn Kelly Show, Kelly speculated that Tamura could have been trying to access the floor for the NFL, but stepped into the wrong elevator bank, a problem that can happen often in high-security NYC skyscrapers, which frequently have elevators segregated by floor ranges."All the elevators and virtually all these highrises, and I've worked in plenty of them, require you to select whether you're going to like floor 1 through 15, or floor 16 through 30, or floors 31 through 44. And depending on which one you want, you get into a different elevator," Kelly stated. "It is possible this shooter wanted to go to the floor that housed the NFL staff, but didn't press the right numbers, went up to the 33rd floor, which is where the management company for the building was."Shane Tamura's NYC shooting leaves 4 dead, NFL employee injuredThe shooter was identified as 27-year-old Las Vegas resident Shane Tamura, who has a history of mental illness. He is listed as a former high school football player at Granada Hills Charter in California, a fact that might have contributed to his fears of CTE.According to Fox News, police found an AR-15-style rifle made from parts, a revolver, extra ammo, and prescription drugs in Tamura’s vehicle. He had legally bought the handgun in Nevada with a concealed carry permit issued in 2022. Detectives are now looking into how he got the rifle parts and if anyone helped him.Shane Tamura killed four people, including NYPD officer Didarul Islam and three civilians. One league employee was confirmed by NFL Commissioner Roger Goodell to have been "seriously injured" in the assault; however, it is not yet known whether the official was a deliberate target when Tamura opened fire.NYPD Commissioner Jessica Tisch confirmed in a press conference that detectives are retracing Shane Tamura’s steps from Las Vegas to New York, including searches of his home and interviews with associates. The motive remains under investigation, but the suicide note provides a glimpse into his mindset.