When Shane Devon Tamura walked into a midtown Manhattan office building with an assault rifle, he also carried a note in his back pocket that provides the only hint at why he opened fire on people in the building. 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. Tamura played