NEW YORK, Sept 27, 2025 (BSS/AFP) - The gunman who carried out a deadly attack at NFL headquarters in New York this summer suffered from the same type of brain injury found among former professional American football players, the city's medical examiner said Friday.

The shooter, identified by police as 27-year-old Shane Tamura of Las Vegas, killed four people at the National Football League offices in midtown Manhattan on July 28 and then shot himself.

Authorities found a suicide note indicating that he suffered from Chronic Traumatic Encephalopathy (CTE). It included the words: "Study my brain please. I'm sorry."

In a statement, New York's Office of the Chief Medical Examiner said that an investigation by neuropathology experts on Tamura had "found unambiguous diagnostic evidence" of low-stage CTE "in the brain tissue of the decedent."

"CTE may be found in the brains of decedents with a history of repeated exposure to head trauma," the medical examiner said.

It noted that the science around CTE was still evolving and that the physical and mental manifestations remained under study.

Tamura had never played for the top professional league, though he was reportedly a star player in high school in California.

He carried out the mass shooting right after driving cross-country from Las Vegas to New York in a BMW, authorities said.

CTE, which cannot be tested for in living individuals, is a degenerative brain disease caused by repetitive head trauma.

It has been linked to an array of behavioral symptoms including aggression, impulsivity, depression, anxiety, paranoia and suicidal tendencies, as well as progressive cognitive symptoms such as memory loss.

Awareness of the condition rose through the groundbreaking work of Dr Bennet Omalu, a Nigerian-American forensic pathologist, who discovered CTE in the brain of former Pittsburgh Steelers center Mike Webster in 2002.

Webster died at 50 after years of erratic behavior and physical decline.