The gunman who killed four people in a Midtown Manhattan office building in July had chronic traumatic encephalopathy, the degenerative brain disease linked to repeated head injuries sustained in football and other contact sports, according to the New York City medical examiner’s office.
The disease, known as C.T.E., can be diagnosed only posthumously. Shane Tamura, the gunman, killed himself after the shooting spree at 345 Park Avenue.
The medical examiner “found unambiguous diagnostic evidence of Chronic Traumatic Encephalopathy, also known as C.T.E., in the brain tissue of the decedent,” according to a statement. “The findings correspond with the classification of low-stage C.T.E., according to current consensus criteria.”
Mr. Tamura, a former high school football player, shot himself in the chest after shooting four people and left behind a note that said his motive was anger at the National Football League, which he blamed for hiding the effects of C.T.E.
The police said Mr. Tamura, 27, drove from his apartment in Las Vegas and arrived in Manhattan targeted the building at 345 Park Ave. because it housed the N.F.L. headquarters became the scene of a shooting spree that left five people dead.
The note, from which the police released excerpts, also inveighed against the National Football League, which has offices at 345 Park Avenue, where the shooting took place, saying it had concealed the danger of the sport in favor of profits.
Mr. Tamura’s family declined to comment on Friday’s findings.
The condition of Mr. Tamura’s brain revives questions about the possible long-term dangers of playing tackle football, even at only the youth level.
Mr. Tamura, who played football in high school but not beyond, carried a note that referred to C.T.E. and claimed that the N.F.L. had concealed the risk of brain trauma in the sport in favor of profits. The police said he was seeking vengeance on the league, whose headquarters are in the building.
As scores of former football players, boxers and hockey players have been found to have C.T.E. over the past two decades, awareness of those sports’ dangers has increased and researchers have learned more about the disease and its symptoms. Leaders of the N.F.L. and other leagues, however, have generally been disinclined to acknowledge the link between their sports and brain trauma.
C.T.E. often affects the superior frontal cortex, an area of the brain that is important for cognition and executive function, including working memory, planning and abstract reasoning. The disease also often affects the amygdala, which is important in emotional control, aggression and anxiety. Common symptoms include problems controlling aggression and impulses, some degree of dementia, mood swings, lapses in judgment and a disorganized manner.
Most cases of C.T.E. have been found in former athletes who played contact and collision sports like football for 15 or even 20 years, and who most likely absorbed thousands, if not tens of thousands, of hits to the head during their careers. Researchers have cautioned, though, that research on C.T.E. suffers from selection bias because most families that donate the brains of their loved ones did so because they were exhibiting symptoms.
As knowledge of the disease has grown, families have donated the brains of younger athletes, and some of them have been found to have C.T.E. as well, albeit at lower rates. These cases have generally been less severe than those found in older athletes. Mr. Tamura, who was 27, joins this growing cohort.
Regardless of age, researchers are wary of linking C.T.E. to specific actions, particularly murder or suicide, because many other factors could have been involved in those decisions.
Dr. Ann McKee, the director of the Boston University C.T.E. Center, who has studied thousands of brains of athletes, soldiers and others exposed to brain trauma, has said that little is known about the link between violent impulsive behavior and C.T.E. and that more studies must be done.
“There is damage to the frontal lobes, which can damage decision making and judgment,” she recently told The Times. “It can also cause impulsivity and rage behaviors, so it’s possible that there’s some connection between brain injury and these behaviors.”
Several high-profile cases in which former football players have committed violent crimes have garnered national attention, most notably Aaron Hernandez, the New England Patriots tight end who was convicted of murder and killed himself in jail. Mr. Hernandez, who died at 27, was found with such a severe form of C.T.E. that the damage was akin to that of players well into their 60s.
Phillip Adams, who fatally shot six people and then himself in Rock Hill, S.C., in 2021, also had an “unusually severe” form of C.T.E. He was 32 and had played six seasons in the N.F.L.
Other former N.F.L. players who committed suicide, most notably Dave Duerson, deliberately shot themselves in the chest to preserve their brains. Duerson left a note asking that his brain be studied.
But researchers note that those individuals do not necessarily represent the broader group of people living with C.T.E.
“I would never draw a direct line between someone’s brain pathology and any specific violent act, because the majority of people who have C.T.E. never committed anything like this,” Dr. Daniel H. Daneshvar, chief of brain injury rehabilitation at Harvard Medical School, recently told The Times.
The risk of developing C.T.E. was long considered limited to those who toiled for years in professional football, rugby or boxing, sustaining an untold number of blows to the head. But more recently it has been diagnosed in younger athletes in a range of contact sports, including some who never played professionally — or, in some cases, did not even play in college.
In a Boston University study released in 2023, researchers examined the brains of 152 contact-sport athletes who died before turning 30 and whose families had concerns about brain disease. Of the 152 athletes studied, more than 40 percent had evidence of C.T.E. Most had played at no higher than the high school or college levels. Of the 63 who died with C.T.E., 48 had played football.
These athletes, like older athletes, were found with a tau protein in certain parts of their brain, a signature of C.T.E. But the tau protein was less concentrated than in older athletes, and the young athletes’ cognitive symptoms were similar to those of other youth athletes who were not found to have had C.T.E. This could mean that the smaller amount of tau was not leading to the symptoms these athletes experienced and that other factors were possibly involved, researchers said.
“The message here is that there’s less scientific understanding of what’s driving the symptoms in these younger players, and whether it’s related to brain trauma or perhaps other things,” said Gil Rabinovici, a professor of neurology and radiology at University of California, San Francisco, who is developing imaging techniques to diagnose dementia and C.T.E. in living patients. “It’s going to be important to look at other brain changes that are not tau related. We should be very cautious in trying to attribute their behavior to what we find in the brain.”
In the absence of a test that can determine if someone has C.T.E., athletes may, like Mr. Tamura, conclude that their cognitive problems are related to the disease. Dr. Rabinovici pointed to a survey of 4,180 former professional football players, 34.4 percent of whom believed they had C.T.E. based on symptoms that included headaches, cognitive difficulties, depression and thoughts of suicide.
Mr. Tamura took prescription medicine for anxiety, depression and bipolar disorder, his mother and police officials in New York said. He scribbled suicide notes showing his obsession with brain injuries. He believed his poor mental health was the product of playing football and repeated knocks to the head.
Dr. Rabinovici and other researchers have been working for years to develop a test for C.T.E. in the living. The most promising techniques include blood tests and brain imaging that can identify the tau protein in specific parts of the brain. The work on a solution is “slow and steady,” he said.
After years of public-relations crises and mounting evidence of a connection between football and C.T.E., the N.F.L.’s top health and safety official acknowledged a link in 2016. The league has steered children away from playing the sport in its regular form, encouraging safer tackling methods and promoting flag football.
Ken Belson is a Times reporter covering sports, power and money at the N.F.L. and other professional sports leagues.
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