Nobody was injured in the Feb. 1 incident outside James "Nikki" Rowe High School in McAllen during a confrontation with another student.
Mission police Chief Leo Longoria confirmed Wednesday that the handgun allegedly fired by the 16-year-old boy, who remains in juvenile custody, was reported stolen Aug. 4 from his city-owned undercover vehicle.
Investigators are trying to determine how the gun ended up with the youth. Serial numbers from the Mission Police Department-issued gun helped identify the weapon.
Longoria says he's relieved and thankful that his weapon was recovered and nobody was hurt.