Yousuf Aziz, 19, was arrested late Wednesday night along with another teenager believed to have been in the car with him when he allegedly shot the victim.
A Pittsburg man who police originally identified as the shooter has been cleared of those charges but remains in custody for allegedly violating his parole, police said.
The shooting was reported at about 8:30 a.m. at Sagebrush Drive near Prewitt Ranch Road, police said.
The victim, who is believed to be a rival gang member, had been walking with a group of people near the high school when they heard loud music coming from a Lexus sedan.
The victim and the people in the car "exchanged words" and then someone in the car fired a gun, Lt. Leonard Orman said.
The victim was airlifted to a local hospital and is expected to survive, police said.
During a re-interview, Aziz allegedly confessed to shooting the teenager and to driving the car used during the incident, police said.
A 16-year-old Antioch boy and a 15-year-old Oakley girl were identified as being passengers in the car during the shooting.
The boy has allegedly admitted to confronting the victim with Aziz, being a fellow gang member, exhibiting gang signs and possessing the handgun used to shoot the victim, police said. He was booked into Juvenile Hall in Martinez.
The girl was not arrested and investigators are not planning to seek charges against her, police said.
Investigators planned to present the case to the district attorney's office today seeking charges against Aziz and the 16-year-old boy.