The Manhattan gunman believed he had CTE. What does that mean?

The gunman accused of walking into a Park Avenue skyscraper in Manhattan and killing four people suspected he had chronic traumatic encephalopathy, or CTE — a degenerative brain disease often associated with football players.

New York City Mayor Eric Adams said 27-year-old Shane Tamura was possibly targeting NFL offices located in the building where police say he shot and killed four people, critically injured another and then fatally shot himself on Monday night.

Tamura played football in high school in California. A 2014 article in the The Santa Clarita Valley Signal called him a notable running back who came “out of nowhere to become one of the most electrifying players in the league.”

Police say a three-page note found in his wallet at the scene requested that his brain be studied for CTE and blamed the NFL for concealing the dangers of football to the brain. Tamura did not play in the NFL.

What is CTE?

CTE is a degenerative brain disease that involves the buildup of abnormal tau proteins, often leading to violent mood swings, suicidal thoughts, dementia and other negative effects.

The condition is often associated with athletes in full-contact sports, particularly football, as it has been linked to frequent concussions and blows to the head.

Doctors are not yet able to diagnose the disease in living patients. But a 2017 study to examine the brains of former football players of all levels revealed that 177 out of 202 had CTE, nearly 88%.

A recently published Harvard University survey of 1,980 retired professional football players who played between 1960 and 2020 found that one-third of them believed they had CTE. More than 230 of the former players reported experiencing suicidal thoughts, and 176 reported a diagnosis of Alzheimer’s disease or another form of dementia.

Researchers in both studies acknowledged that selection bias could have been a factor, in that families of deceased players with health problems or former players with health issues could have been more motivated to participate.

Boston University researchers said in 2023 that they had posthumously diagnosed 345 former NFL players with the disease.

The NFL and CTE

Former players and advocacy groups have been critical of the NFL for the role the organization has played in allegedly suppressing CTE research. In 2016, a congressional committee found the NFL “attempted to influence the grant selection process” for a study on brain injury.

Forensic pathologist Bennet Omalu gained attention for his findings of CTE in a 2002 autopsy of a former NFL player. He told NPR that the NFL responded to his research by accusing him of fraud.

A 2009 GQ Magazine exposé reported on Omalu’s research and the pushback he received. In 2015, the story was turned into a Hollywood film that helped mainstream the issue and caused many fans to question the safety of the nation’s most popular sport.

Former players who sued the NFL have accused the league of trying to minimize the public’s perception of the risks of head trauma. In 2016, a federal appeals court upheld a major settlement between the NFL and thousands of retired football players with neurological disorders.

In the note left behind at the scene of the Manhattan shooting, Tamura referenced the 2005 suicide of former NFL player Terry Long who was revealed to have been living with CTE.

“You can’t go against the NFL,” Tamura wrote, according to police. “They’ll squash you.”

The NFL has responded to criticism about how it protects its players from head trauma by instituting rules for when a player is suspected of having suffered a concussion. The league says it enforces a five-point protocol before players can return to the field after a concussion, and the checklist is reviewed every year.

It also is expanding the use of new helmets that the league says reduce concussions.

A spokesperson for the NFL did not immediately return a request for comment on the shooting and CTE.

Violence and CTE

Many brains of former NFL players who have died by suicide have been found to show signs of CTE.

In 2011, former NFL player Dave Duerson killed himself, leaving behind a request that his brain be studied for signs of CTE. Researchers at the Boston University Center for the Study of Traumatic Encephalopathy found Duerson had suffered from an advanced form of the condition.

A year later, retired linebacker Junior Seau died in the same manner, and his family requested that his brain be studied for the disease. Researchers said his brain had “cellular changes consistent with CTE.”

In one high-profile case, former New England Patriots player Aaron Hernandez, who had a history of violent and aggressive behavior, was found guilty in 2015 of first-degree murder.

Two years later, he was found having killed himself in his jail cell at age 27, and his brain revealed one of the most extreme cases of CTE documented in a person his age.

If you or someone you know may be considering suicide or is in crisis, call or text 9 8 8 to reach the Suicide & Crisis Lifeline.