The New York City Office oftheChief Medical Examiner determined that Shane Tamura, the Midtown mass shooter, had low-stage Chronic Traumatic Encephalopathy, also known as CTE.

"CTE may be found in the brains of decedents with a history of repeated exposure to head trauma. The science around this condition continues to evolve, and the physical and mental manifestations of CTE remain under study," the Medical Examiner's Office wrote in a statement.

Tamura shot and killed four people and injured an NFL employee before he turned the gun on himself on July 28.

He opened fire inside a Park Avenue building, that is home to the NFL headquarters.

Investigators believe he was targeting the NFL. They found a note in his pocket, where he claimed to have CTE and requested his brain to be studied.

Tamura played high school football and had a documented history of mental health issues.

Investigators say in letters left behind, he expressed anger that his mental struggles could have been associated with playing football.

Doctors caution attributing the connection of his actions to the disease.

"I see the notion propagated that playing a contact sport causes a person to have symptoms that are irrevocability progressive and that lead to behaviors such as the devastating consequences that we saw in this case," said Dr. Kristen Dams-O'Connor, director of the Brain Injury Research Center at Mount Sinai.

The OCME says that CTE may be found in the brains of people after they died who had a history of repeated head trauma.