Charlie Stevens death: South Australian Police Commissioner Grant Stevens and his wife recall the heartbreaking final words to their teenage son killed in a hit-and-run

South Australia's top cop and his wife have opened about the heartbreaking loss of their youngest child and their parting words to their beloved son in his final moments.

The pain for Police Commissioner Grant Stevens and his wife Emma is still brutally raw seven months on from the unimaginable tragedy that rocked their family forever.

Charlie Stevens, 18, was with friends waiting for a bus to head to Schoolies celebrations when he was struck by a car driven by Dhirren Randhawa in Goolwa, south of Adelaide, on November 17 last year.

Charlie was airlifted to Flinders Medical Centre but died the next day from a severe brain injury surrounded by his family.

Commissioner Stevens and his wife wept as they revealed their final words to Charlie in a powerful 60 Minutes interview which aired on Sunday night,

'Some things I won't repeat 'cause I was cross with him!' Mrs Stevens recalled.

'I just think I said, 'Love you. 'You're my baby and you always will be.''

Commissioner Stevens added: 'It was good to spend time with him, but the hardest thing was leaving for the last time.'

The couple acknowledged that it's not only their lives that have been changed forever, but also the driver who killed their son.

They expressed remarkable compassion and forgiveness for Rhandhawa, who was also 18 and on his P-plates at the time.

 'You know he's going to have to live with this his whole entire life,' Mrs Stevens said.

'I think being a parent, being a mum of an 18-year-old, they're not that smart. They're 18.

'And I look at it and I think it also could have been Charlie.'

Rhandhawa was initially charged with causing death by dangerous driving, aggravated driving without due care, leaving the scene of a crash after death and failing to truly answer question.

However, in a plea deal, he admitted to a charge of aggravated driving without due care and leaving the scene of a crash.

He will face court next month for sentencing.

Rhandhawa's admission of guilt will save the Stevens enduring the pain of a trial.

'We're grateful for the fact that Dhirren has pleaded guilty,' Commissioner Stevens said.

'It gives us some understanding of the acceptance of his responsibility.'

Rhandhawa penned a letter of apology to the Stevens for which they are very grateful.

'We appreciate it, we appreciate the fact that he's given us that apology,' Commissioner Stevens said.

'We think that's, obviously, it gives us some understanding of his acceptance, of his responsibility. 

But I think with what is left to occur in the court process, we'll just let that unfold.'

His wife added: 'And [that] he's written it, and that it's words from an 18-year-old,' Mrs Stevens said.

'I don't think he's been sat down and told what to write. I think it's him.'

Ms Stevens then joked: 'In fact, I'm not so sure Charlie would be able to write something quite as good as that!' 

Commissioner Stevens admitted that he never thought his family would be the one to hear the news a loved one had been killed.

'I always thought that delivering a death message was the hardest thing police officers have to do,' he told the program.

'And as much as you empathise with the families that you give that information to, you have no concept, no appreciation of just how tragic it is, and how it just rips your guts out.

'You never think it's going to happen to you.'

The couple also revealed that Charlie was an organ donor and that his death gave seven people a second chance of life.

They looked back on Charlie's memorable service that was attended by nearly 2,000 mourners, celebrating Charlie's life.

Instead of sending flowers, the Stevens family requested mourners make donations to Operation Flinders, an outback adventure therapy program that has been running for more than 30 years. 

In that time, Operation Flinders has so far helped 10,000 at-risk teenagers.

In an overwhelming response, close to $220,000 has so far been raised in Charlie's name as his legacy continues.