Originally Published: 12 OCT 22 01:49 ET

Updated: 12 OCT 22 16:38 ET

By Nouran Salahieh, Andy Rose and Amanda Musa, CNN

(CNN) -- The former San Antonio police officer who was charged and arrested Tuesday in the shooting of an unarmed 17-year-old at a McDonald's parking lot was released early Wednesday on bond, according to the Bexar County Sheriff's Office.

James Brennand turned himself in Tuesday night on two charges of aggravated assault by a public servant. He was released at 4:03 a.m. CT after posting $100,000 bond for each count, the sheriff's office said.

The October 2 shooting, which left teenager Erik Cantu in critical condition, was a "failure for one individual police officer," the San Antonio police chief said Tuesday. He has since been fired.

The incident began when Brennand, a probationary officer with seven months of experience, responded to an unrelated disturbance call at the restaurant and saw a car he believed had evaded police the day before.

Body camera footage released by police shows the officer walked up to the driver's side of the car, opened the door, and ordered the driver out. The visibly startled teen, holding a yellow McDonald's wrapper, put the car in reverse and started backing up.

The police officer then opened fire five times on the car, according to the video. As the driver shifted the vehicle to move forward, body camera video showed the officer opening fire an additional five times as the car drove away.

The teen, identified as Cantu, was shot multiple times and is in critical condition. He remains on life support and is non-responsive, but his oxygen levels are showing an improvement, his family said Wednesday.

"We are being patient and optimistic that better health is coming. Please continue to keep Erik in your thoughts and prayers," the family's statement read.

Brennand did not respond to requests for comment from CNN prior to his arrest. CNN reached out to a law enforcement advocacy group that represented Brennand in initial proceedings and it declined to comment.

Officer charged with aggravated assault

Chief William McManus said Brennand was charged with one count of aggravated assault for each person who was in the car -- the teenager in the driver's seat and a passenger.

The shooting was "unjustified, both administratively and criminally," and went against the department's policies, McManus said.

"This was a failure for one individual police officer. It had nothing to do with our policies. Policies did not allow that, our training did not teach that. So this was a fail for one particular police officer," the chief said.

The police department has been in contact with the district attorney's office, which may need more information before it takes the case to the grand jury, the chief noted.

"We worked on this for several days to get to this point where we could submit a warrant to a judge for signature, and that's where we are right now," McManus said.

Speaking earlier Tuesday to CNN's Brianna Keilar, McManus said he arrived to the shooting scene and recognized an issue immediately.

"You can tell by looking at the vehicles, which way the vehicle is moving when the shots are fired, and this vehicle, it was very telling to me, that this vehicle was moving away from the officer, and moving parallel with the officer, so it was pretty clear to me at that point that we were going to have an issue," McManus said.

The body camera footage also showed the officers' actions weren't in line with training, according to the chief.

"The video was horrific," McManus said. "There is no question in anybody's mind looking at that video that the shooting is not justified."

McManus said department policy prohibits officers from shooting at moving vehicles, unless their life or someone else's life is in immediate danger.

The teenager, Cantu, was initially charged with evading detention in a vehicle and assaulting the officer, after Brennand claimed he was struck by the door of the car as the teen backed up. But Bexar County District Attorney Joe Gonzales later said in a statement that "the facts and evidence we have received so far led us to reject the charges against Erik Cantu for further investigation."

After the shooting, the teen was found a block away suffering from multiple gunshot wounds, while a passenger in the car was uninjured, police said.

The chief has said the aggravated assault charges could rise to homicide if the 17-year-old does not survive.