Ex-footballer made chilling four-word comment in note 'left at scene' after shooting dead four people at NFL HQ

An ex-footballer who is suspected of killing four people near the NFL headquarters left a four-word note at the scene, it has been reported.

Shane Devon Tamura, 27, entered 345 Park Avenue, a 634-foot skyscraper that housed the NFL headquarters, on Monday, according to New York City authorities.

It is said that he possessed an M4 rifle and opened fire in both the lobby and the 33rd floor, before then killing himself. Police are yet to determine a potential motive for the attack.

Tamura is believed to have driven cross country 'for days' from his home in Las Vegas, Nevada, before reaching Manhattan.

Five people, including the gunman, were killed in the attack, with NFL commissioner Roger Goodall stating that an NFL employee has also been seriously injured.

Law enforcement have stated that Tamura had a 'documented mental health history'.

The 27-year-old was a former high school football player and played as a running back, with his coach telling the Los Angeles Times in 2015 that he was 'looking for big things' from him.

NYC gunman 'left four-word note at scene' as four people killed

According to CNN, Tamura left a chilling letter at the scene of the attack.

It is alleged that he claimed that 'playing football gave me CTE' and added: "Please study my brain."

CTE, full name chronic traumatic encephalopathy, is a neurodegenerative disease which is caused by repeated blows to the head and concussions.

The disease can lead to behavioural and mood issues, and cause sufferers to act aggressively or irrationally.

However, CTE can currently only be officially identified through a post-mortem, meaning sufferers cannot be diagnosed while alive.

In 2015, the NFL promised to compensate players who had developed dementia, or other brain-related injuries or diseases, developed through concussions.

The Washington Post claimed last year that, while over 1,600 athletes have received a cumulative payout of $1.2 billion, a number of other claims - reported to be 28 per cent - have been rejected by the NFL.