The fight broke out at the Alburgh Community Education Center in Alburgh ... during a hoops game that involved seventh and eighth-grade boys from Alburgh and St. Albans middle schools.

Video that was shot from the alleged scene shows several adults rushed onto the court -- kicking and punching each other -- all while the kids looked on from the sidelines.

It's unclear what sparked the melee ... Vermont State Police said in a statement Wednesday that when officers showed up to the scene just before 7 PM, the fracas had ended and several people involved in the tiff had already left the school.

Cops say Russell Giroux was injured during the fight, but elected to drive home. Giroux ended up stopping his car and calling first responders, and was transported to a nearby hospital. Tragically, he was pronounced dead at the medical facility. His body, cops say, will undergo an autopsy to determine the cause and manner of his death.

The VSP says it's now investigating the circumstances surrounding it all -- though no arrests have been made yet. They're asking anyone with information to come forward or call the Detective's Office at the St. Albans Barracks at 802-524-5993.

Both schools released statements Wednesday on the incident ... calling it all heartbreaking.

"All of us in the Maple Run Community are shocked and saddened by last night’s death of Russell Giroux after a physical altercation during a basketball game at the Alburgh Community Education Center," Alburgh M.S. officials said.

"We extend our condolences and sympathies to his family and friends. Since our students observed the altercation, we are working in the next days to support our students and families in dealing with the consequences of the altercation and Mr. Giroux's death."