Tributes have already begun pouring in for the late athlete.

Colt Brennan was a star QB from a very young age.

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He first began his career in high school at Mater Dei.

He really came into his own at the University of Hawaii.

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​He finished 3rd in the Heisman Trophy 2007 after completing 359 passes for more than 4,300 yards and 38 TDs - making him one of the best college QBs that year.

Following college, Brennan was drafted in the 6th round of the 2008 NFL Draft by the Washington Football Team.

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He then played at the Raiders before bouncing to the Canadian Football League, followed by a short stint with the L.A. Kiss of the Arena Football League - but his career never truly took off.

Since then, Brennan has had a hard time, facing legal troubles and car accidents.

"I've been through a lot in my life. I was a convicted felon for a crime I never committed, (passed polygraph and all). I captured every dream I had as a child," he shared on Instagram.

"I was drafted into the league only to have 2 knee and 2 hip surgeries. I reached my 3rd year in the NFL, only to awake from a coma with traumatic brain injury as a passenger in a car accident."

"I battled drug and alcohol abuse, and eventually developed blood clots years after the car accident."

"I spent 9 months in the hospital and for the last 2 1/2 years have been trying to learn how to walk again with a broken heart."

"I found redemption once, I will find it again. They say: 'Some people are just born to fight, and it's not their born brave or born strong. It's just that the Universe decided that this one, this one will have the grit and fire, and the steel in their blood. They will be tested this cosmic mettle of theirs. They will face trial after trial, be broken and damaged in countless ways, but this one was born to fight.'"

But tragically, TMZ has confirmed that Brennan has died aged thirty-seven.

He was found unconscious at the rehab center he was staying in in Southern California.

"He was doing so well, the spark was back in his eyes, and he was healthy and doing great, and it happened," dad Terry said.

"These guys [at the rehab facility] were no-nonsense guys. It just got away from him. I don't know how else to explain it. Maybe one day I'll be able to explain it better."

"He went peacefully ... He listened to Bob Marley. His sisters had a lei around him when he was unconscious. They had the music of Bob Marley playing near his ear."

Rest in peace.