Charlie Stevens, 18, sustained an irreversible brain injury after being run down about 9pm on Friday in Goolwa, about 90km southeast of Adelaide, an emotional SA Police Deputy Commissioner Linda Williams told reporters.
Police say the 18-year-old driver failed to stop at the scene but was found nearby.
He has been charged with causing harm by dangerous driving, aggravated driving without due care, leaving the scene of a serious crash and failing to truthfully answer questions.
The man has been refused bail and will face Christies Beach Magistrates Court on Monday.
Premier Peter Malinauskas said the thoughts of all South Australians were with the commissioner.
Premier Peter Malinauskas said the thoughts of all South Australians were with Commissioner Grant Stevens, his wife Emma and their children.
"Grant Stevens has served South Australia as a member of South Australian Police for over 40 years," Mr Malinauskas said.
"His whole life he has dedicated himself to protecting others, protecting South Australians from evil, protecting us from disease.
"He has shown extraordinary leadership in some of the most difficult circumstances this state has ever confronted, and it is just so unjust that he and his family have now had to endure this great tragedy themselves."
Ms Williams said Charlie was an apprentice carpenter who had recently finished school.
It was unclear what brought the 18-year-old alleged offender to Goolwa, but Charlie was there celebrating schoolies with his friends.
"He is with his family who are waiting for other family members from interstate to arrive," the deputy commissioner said.
"As you can imagine, this is a very difficult statement for me to make.
"We always talk about this happening to other people but the reality is it can happen to anyone."
Charlie sustained an irreversible brain injury and he is currently on life support.— Peter Malinauskas (@PMalinauskasMP) My thoughts are with Police Commissioner Grant Stevens, his wife Emma and their family, Charlie's friends and work mates. Grant and Emma are two of the most decent people I know.November 18, 2023
The alleged hit-run was the second incident to plunge the South Australian policing family into mourning on Friday.
Mr Malinauskas said he was discussing the fatal shooting of Brevet Sergeant Jason Doig at Senior, in SA's southeast, with Mr Stevens just hours before the commissioner learned of his son's involvement in the Goolwa collision.
The premier said it struck him just how determined Mr Stevens was in ensuring the welfare of his colleagues in the wake of the deadly shootout.
"To the young people in our state, all of your lives are precious," Mr Malinauskas said on Saturday.
"It is just so important that we all remember that in a moment of complete stupidity or an impulsive act, the consequences can be so incredibly severe for everyone around you."
Major crime detectives continue to investigate the Goolwa incident.
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