A 17-year-old NBA fan suffered catastrophic head injuries after falling from a moving vehicle while celebrating a San Antonio Spurs playoff victory.

The unidentified teenager is in critical condition and is brain dead following the incident, which occurred during celebrations after the Spurs’ Game 6 win over the Oklahoma City Thunder on Thursday, News 4 San Antonio reported.

According to relatives, the boy was celebrating the victory — which forced a decisive Game 7 in the Western Conference semifinals — when he fell from the vehicle and struck his head.

He was initially rushed to an emergency room and later transferred to another local hospital due to the severity of his injuries.

The teenager is brain dead and is not expected to survive, a police source told the San Antonio Express-News.

The exact circumstances of the incident remain under investigation.

“The San Antonio Police Department extends our sympathy to the family, friends, and loved ones affected by this tragic and preventable incident,” the SAPD said in a statement.

“This serves as an important reminder that public safety is a shared responsibility. We encourage everyone celebrating to follow traffic laws, stay inside their vehicles, and follow directions from the officers who are there to keep everyone safe.”

The Spurs defeated the Thunder on Saturday night to advance to the NBA Finals, where they will face the Knicks.