In brief
The gunman, Shane Tamura, who killed four people in a Manhattan office building, had been diagnosed with low-level chronic traumatic encephalopathy (CTE), as confirmed by New York City's medical examiner. Tamura left notes blaming the NFL for concealing the impacts of CTE. He had known mental health issues and requested his brain be studied posthumously. The tragedy highlights the ongoing concerns surrounding CTE, particularly in relation to former athletes.
The gunman who killed four people in a Manhattan office building had chronic traumatic encephalopathy (CTE), a degenerative brain disease often linked to high-contact sports like American football, according to the New York City medical examiner's office.
In July, Shane Tamura, 27, drove from Las Vegas to New York City with an assault-style rifle, shooting four in a Park Avenue skyscraper before killing himself.
Police believe he was targeting the offices of the National Football League (NFL), which were inside the building.
In notes left at the scene, Tamura reportedly blamed the NFL for concealing the effects of CTE and asked for his brain be studied.
CTE can only be diagnosed post-mortem.
New York City's chief medical examiner said the shooter's autopsy confirmed that he had low-stage CTE and the diagnosis was unambiguous.
The disease is caused by repeated blows to the head and has been found in the brains of dozens of former NFL players. Science around it is evolving, the medical examiner said. It is associated with symptoms including memory loss, depression and progressive dementia.
The physical and mental manifestations of CTE remain under study, they said.
Tamura, a former high school football player who did not play in the NFL, opened fire in a building where the American football league headquarters was located. But he took the wrong lift and went to a different part of the building.
His alleged suicide note said study my brain please, according to a senior official who spoke to ABC News. I'm sorry, he also wrote.
Police say Tamura was known to have mental health issues.
Among those killed during the mass shooting were NYPD officer Didarul Islam; Wesley LePatner, an employee of finance giant Blackstone; and Julia Hyman, an employee at Rudin Management.
NFL employee Craig Clementi was also seriously injured.
