Recently, a video of the shooting has surfaced, shocking viewers.
James Brennand had only been a probationary officer with the agency for seven months.
The incident happened on October 2.
Initially, Brennand claimed that he fired at the teen's automobile after it struck him.
Body camera footage of the incident has now surfaced, and it contradicts his account.
An SAPD report states that Brennand responded to a disturbance complaint at 10:45 p.m. on Sunday, October 2, and tried to interview witnesses when he saw a car that had eluded him the day before while he was attempting a traffic check because the registered license plate didn't match the car.
According to the report, the earlier event had nothing to do with the restaurant disturbance call.
Brennand then walked over to the automobile and opened the door.
Brennand could be seen on the footage opening the door of the red car that was parked in a McDonald's lot.
Brennand made a help request, walked up to the car, and unlocked the driver's side door.
The vehicle was occupied by Erik Cantu and an unidentified 17-year-old female passenger.
"Leave the automobile now!" Cantu, who was eating a McDonald's burger, was informed by Brennand.
"Why?" Cantu questioned as his car started to revers.
Brennand answered by repeatedly shooting his rifle.
At least ten shots were fired, and four of them struck Cantu.
Cantu was sent to a local hospital, where he is allegedly making a full recovery.
According to reports, the nameless passenger was unharmed.
Cantu has been accused of escaping arrest in a car and assaulting a police officer.
Brennand was fired by the San Antonio Police Department on Wednesday, October 5.