Nat Barr breaks down in tears live on air - forcing producers to abruptly cut to an ad break

Sunrise host Nat Barr has broken down into tears while live on air - forcing producers to cut to an ad break. 

Her tearful outburst came after an emotional letter was read from South Australia Police Commissioner Grant Stevens, whose son Charlie died after suffering an irreversible brain injury when he was allegedly hit by a car on Schoolies. 

The hosts heard that Commissioner Stevens had signed off the heartfelt note by saying his son's death meant so much more than just a number on a tragic tally. 

Barr seemed unable to speak as she choked back tears with her co-host Matthew Shirvington, known by viewers as Shirvo, forced to take over the segment. 

The story had a particular impact on Barr, who has two teenage sons named Lachlan and Hunter. Hunter, having completed high school earlier this year, would have been celebrating schoolies week at the time the police commissioner's son died. 

'I've got to be honest with you, it's extremely hard to get through without shedding a tear even though whether you knew Charlie or you didn't know him,' Shirvo said. 

'The understanding of losing a teenage child, Nat and I are in that position with teenage kids, it's extremely difficult.'

Shirvo, who also appeared to be getting emotional, then read a line from the letter. 

'You lived a life and gave so much to so many. You're a force of nature, we'll never forget your beautiful, cheeky, disarming smile.'

Her voice breaking, Barr added: 'Well said Shirvo. We'll be back in a moment.' 

The letter from Commissioner Stevens described how loved Charlie was. 

'I am writing this sitting in a bedroom with dirty clothes on the floor, an unmade bed, six drinking glasses lined up on the bedside table, an empty KFC box next to the glasses, wardrobe doors left open and a row of skateboards leaning on the wall – it is a mess and it's perfect. This is where 101 lived,' he wrote. 

101 refers to the 101st life lost on South Australian roads this year. 

'101 is Charles Stevens – Charlie, Charlie Boy, Chas, Links, Steve. You lived life and gave so much to so many. You were a force of nature and we will never forget your beautiful cheeky, disarming smile,' Commissioner Stevens said.

'Son, brother, grandson, uncle, nephew, cousin, friends, workmate, teammate. So much more than just a number on a tragic tally.'

Charlie Stevens, 18, was with friends waiting for a bus to head to Schoolies celebrations in Victor Harbor when he was allegedly struck by Dhirren Randhawa, also 18, in Goolwa, south of Adelaide, about 9pm on Friday.

Mr Stevens died 22 hours later in hospital, while Mr Randhawa was arrested a short time later on a nearby street after allegedly fleeing the scene.

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

More to come.