• Shane Tamura, the gunman, was diagnosed with low-stage CTE post-mortem.
• He targeted the NFL headquarters, blaming the organization for concealing brain injury risks.
• Four people were killed in the incident, including a police officer.
• Details from a suicide note revealed his grievances against the NFL.
• The NFL has acknowledged a connection between football and CTE since 2016.

Shane Tamura, who killed four people in a shooting at the NFL headquarters in Manhattan, was diagnosed with low-stage Chronic Traumatic Encephalopathy (CTE), as confirmed by the New York City Medical Examiner's Office. The examination revealed "unambiguous diagnostic evidence" of the degenerative brain disease typically associated with concussive and sub-concussive impacts experienced in contact sports like football, according to SFGate, India Times, and BBC.

On July 28, Tamura drove from Las Vegas to New York City with an AR-15-style rifle, targeting the NFL headquarters. He entered the building but took an incorrect elevator, leading him to a different floor where he fatally shot two security personnel, including NYPD Officer Didarul Islam, and two others before taking his own life, as specified in reports from LA Times and Reuters.

In a three-page suicide note, Tamura expressed his belief that he suffered from CTE due to his high school football career and accused the NFL of prioritizing profits over player safety. He wrote, "Study my brain, please. I'm sorry," highlighting his grievances against the organization, according to LA Times and India Times.

Authorities have revealed that CTE can only be definitively diagnosed post-mortem and that its effects on behavior and mental health remain a significant area of study. The connection between football-related head trauma and CTE has been a point of contention, with the NFL having previously denied any relationship until it acknowledged the link in 2016, as detailed by Reuters and BBC.