Cops say after the parties were separated, some of the people involved got into a car and started shooting backward while speeding off. Unfortunately, according to cops, one of the bullets struck Pastrana.
A bystander captured the whole thing on camera ... showing everyone running for cover when several gunshots rang out.
"The motive and circumstances involving this incident remain under investigation," authorities said in a statement this week.
Head coach Mike Wilson III told the Times-Heraldthe team found out about Pastrana while suiting up for practice and they took "the news very hard."
"When we found out what happened all practices were canceled," Wilson said. "When it was safe we told everyone to go home."
Wilson said Pastrana is in stable condition at a local hospital.
VP Police Chief Shawny Williams praised Pastrana for his heroism ... saying, "This is a very courageous staff member that potentially saved another child’s life or multiple people’s lives."
Authorities are asking anyone with information about the case to contact the Vallejo Police Department Detective Division at 707-648-4524.