'Friday Night Lights' Coach Gary Gaines Dead At 73

Legendary H.S. football coach Gary Gaines -- who was portrayed in the iconic "Friday Night Lights" book and film -- has died after battling Alzheimer's, his family announced Monday.

He was 73.

"Following a long battle with Alzheimer's Disease, it is with great sadness that the family of Coach Gary Gaines announces his peaceful passing this afternoon," his family said in a statement.

"Memorial plans will be announced in the coming days. Thank you for remembering our family in your thoughts and prayers."

Gaines -- whose coaching career ultimately spanned over four decades -- got his start at Petersburg High School in Texas in 1977 ... but he's most known for his time at Permian H.S.

In 1980, as an assistant under head coach John Wilkins at Permian, Gaines helped lead the team to the Texas 5A state championship.

Gaines, though, will be most remembered for how he was portrayed in "Friday Night Lights" -- the book/movie about the journey of the 1988 Permian High School football team that marched toward a championship.

Gaines enjoyed tremendous success during his stint at Permian ... leading the team to a perfect 16-0 season and the 1989 5A state championship.

"Friday Night Lights" received an ESPY for "Best Sports Movie" in 2005 and won "Movie of the Year" that same year. Billy Bob Thornton famously portrayed Gaines in the flick.