Tamura killed four and badly wounded another before shooting himself in the chest.In the note, Tamura claimed to have CTE—chronic traumatic encephalopathy, a brain injury condition due to repetitive trauma to the brain—and that he wanted researchers to study his brain.

Chronic traumatic encephalopathy, or CTE, is a brain disease linked to repeated hits to the head, often seen in military veterans and athletes.

Shane Devon Tamura — the man who killed at least four people in a New York City office building — claimed in a suicide noted that he suffered from chronic traumatic encephalopathy (CTE) while slamming the NFL. “Study my brain please,” Tamura, a former high-school football player, wrote in the note. "I'm sorry."