Shane Tamura, Midtown gunman, claimed he suffered from CTE, left a note in his pocket

MANHATTAN, New York (WABC) -- The 27-year-old man who shot and killed four people at a Midtown office building on Monday carried a note in his pocket claiming he suffered from CTE, asked that his brain be studied and made references to the NFL.

The suspect, Shane Tamura, who the police said has a documented mental health history, played high school football in Los Angeles but did not play professionally.

A former teammate of his spoke to our sister station KABC about Tamura.

"He was a great teammate. He was a great guy in general. He didn't cause any problems actually at all in the locker room or on the field," he said. "He was just a guy who really enjoyed the sport, not problematic at all so when I found out the news, I was really shocked, I really couldn't believe it."