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

"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.

Suspected gunman Shane Tamura had a ‘documented mental health history’ and ‘sprayed’ the Manhattan office building lobby with a military-style assault rifle, police say

Authorities also found a vehicle with Nevada plates registered to Tamura at the scene, with a rifle case inside, sources said.

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.

No motive has been announced. A suicide note was found expressing grievances with the NFL and saying Tamura suffered from CTE, a source said. Follow for live updates.

Shane Tamura, who shot and killed four people in a Manhattan office building, once worked surveillance for a Las Vegas casino. In a suicide note, the 27-year-old referenced CTE and claimed the NFL "failed" him.

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,