"Compared to what's on the news, I don't think any one of us, none of my teammates, sensed anything like this from Shane," the former teammate told The Post.

Tamura was involuntarily held after being considered a danger to himself or others, according to a law-enforcement official.

Wearing body armor and wielding an assault-style rifle, the alleged gunman burst into a Midtown Manhattan office building shooting victims at random.

Shane Tamura, the Park Ave. gunman who killed an NYPD officer and three others before taking his own life, left behind a suicide note saying he suffered from CTE, a brain injury often linked to playing football, police sources said Tuesday.