The family of a young San Antonio Spurs fan - who was declared 'brain dead' following a tragic accident while celebrating a recent playoff win - have shared a heartbreaking update on his condition. 

Last Thursday, Jose Luis Rodriguez III, 17, fell from a vehicle during wild celebrations after the Spurs won Game 6 of the Western Conference Finals against the Oklahoma City Thunder.

The teen was driven to a freestanding emergency room before being transferred to a trauma center due to the severity of his injury, where he was declared brain dead.

Family members were told that the 17-year-old was not expected to survive but, despite the worrying assessment, his family insist the teen is still 'fighting for his life'.

Rodriguez's paternal grandmother told KSAT: 'I believe in God and I believe in miracles. I'm trying to hold on for my son, my daughter-in-law and the rest of the family'.

She also revealed that the teenager's organs are still functioning despite his critical head injuries. 

According to the San Antonio Express News, Rodriguez was sat in the passenger-side window of a vehicle when it it a curb and he fell out, striking the pavement. 

The outlet also revealed that the 17-year-old is a student at Frank Tejeda Academy in the Harlandale school district and was set to graduate next year. 

Police reports say the teen was celebrating near Southwest Military Drive - a hotspot for the traditional 'honking' celebrations.

In a statement, San Antonio Police extended sympathy to the victim's family, friends and loved ones - calling it a 'tragic' and 'preventable' event.

'We encourage everyone celebrating to follow traffic laws, stay inside of your vehicles and follow directions from the officers who are there to keep everyone safe,' SAPD said in a statement.

San Antonio's tradition of 'honking' celebrations dates back to the Spurs' 1999 run to the NBA title and grew when the team became a dynasty under Gregg Popovich. 

Fans clad in black-and-silver take their vehicles to certain spots in the city - particularly on Commerce Street in downtown and on Southwest Military Drive on the city's South Side - after victories.

The tradition has led to large gatherings and street parties in the early hours as fans flocked to celebrate major victories for the team in the playoffs.

This incident came one game before the Spurs beat the Oklahoma City Thunder in Game 7 of the Western Conference Finals to reach their first NBA Finals in 12 years. 

They'll play the New York Knicks in a rematch of the 1999 championship series.