11:08 AM PT -- Colt was found unconscious at a rehab facility in Southern California a few days ago, his father Terry Brennan told The Star Advisor.
He was transported to Hoag Hospital in Newport where died on Monday.
Colt had been in a rehab program for the past 5 months to work on his sobriety when something went terribly wrong.
"He was doing so well, the spark was back in his eyes, and he was healthy and doing great, and it happened,” Terry told the outlet.
"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."
Colt was surrounded by family and loved ones when he passed.
"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."
RIP
Colt Brennan -- a former NFL quarterback who was a superstar in college -- has died. He was only 37 years old.
TMZ Sports has confirmed Brennan was in Southern California at the time of his death -- though the cause has not been revealed. We're working on it. Hawaii News Now broke the story.
Brennan was a star QB in high school, backing up Matt Leinart at Mater Dei.
But, he really broke out at the University of Hawaii where he developed into one of the best college QBs in the country.
In fact, Brennan finished 3rd in the Heisman Trophy voting in 2007 -- when he completed 359 passes for more than 4,300 yards and 38 TDs.
Dude balled out that year.
Brennan was selected in the 6th round of the 2008 NFL Draft by the Washington Football Team but never really caught on.
He had a quick stint with the Raiders before bouncing to the Canadian Football League ... followed by a short stint with the L.A. Kiss of the Arena Football League.
Just last month, Brennan wrote a detailed IG post reflecting on his life ... addressing a sexual misconduct allegation during his time at the University of Colorado (before he went to Hawaii).
Brennan was accused of exposing himself to a female student during a drunken bender.
Brennan denied the allegation -- though he was eventually convicted of felony burglary and trespassing and spent a week in jail.
Brennan was ordered to take a lie detector test about the sexual misconduct which he "passed."
He was also involved in a bad car accident (2010) and later arrested for DUI (2012 and 2019) -- all of which he addressed in his April 12 post.
"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."
"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."
Brennan continued, "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.'"
Originally published -- 10:16 AM PT