A 17-year-old was declared legally 'brain dead' after suffering a horrific fall during celebrations for the San Antonio Spurs' win in Game 6 of the Western Conference Finals last Thursday.

The victim, who was not identified, was riding on top of a vehicle during a so-called 'honking' celebration on the south side of the city, according to the San Antonio Express-News.

Police reports say the teen was celebrating near Southwest Military Drive - a hotspot for the traditional 'honking' celebrations - when he fell from that vehicle and suffered a severe head injury.

The teen was driven to a freestanding emergency room before being transferred to a local trauma center due to the severity of his injury, per the Express-News. 

A police source told the outlet that the teenager was not expected to survive.

The fall, and what led to it occurring, are being investigated.

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.

Within the rowdiness, it's common for people to ride on top of vehicles, hanging out of windows or standing in truck beds. Those not riding in vehicles can often be seen dancing in the streets. Other risky behaviors like the lighting of fireworks also takes place.

Police have bulked up numbers in areas where 'honking' celebrations are common to keep the flow of traffic going and to prevent dangerous behavior.

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 re-match of the 1999 championship series.