Scott Pollock had just basic first aid training, but when he was confronted with a scene of carnage outside his home on Thursday night he knew calmness would be key.
Mr Pollock and his partner, Kirsty Edwards, were at their Queanbeyan home on Bungendore Road when they heard a "huge" bang about 8pm and ran outside.
A Honda Accord travelling west, down the hill of Bungendore Road towards Queanbeyan, had slammed into a large sign, then a tree, tearing the car in half and leaving a trail of debris that Mr Pollock said could later be found more than 100 metres from first impact.
"It was so loud I thought it was a truck. Straight after the bang you could hear so many doors opening," Ms Edwards said, as people rushed out on to the street.
Twenty-three-year-old Mr Pollock and 21-year-old Ms Edwards said they were among the first people on the scene, and their immediate reaction was to begin looking for the driver.
"Instinct just sort of kicked in," Mr Pollock said. "I started at the tree and was working my way through all the rubble … and then I heard somebody moaning."
The driver, a 32-year-old man, had been thrown about 40 metres from the wreckage. His leg had been severed, his arm partially severed, and his pelvis smashed.
Being Queanbeyan's late-night shopping night, and with the crash so near one of the town's busier intersections, the crowd grew quickly.
Ms Edwards said people were hesitant to get too close. "Most people around us were freaking out. It was a pretty gruesome thing to see and look at."
Mr Pollock said the driver was conscious and speaking, despite his injuries. With basic first aid training, Mr Pollock said he knew the main priority would be to try to keep the injured man still and calm.
"I was talking to him and taking his mind off what just happened. Another bloke came up and just put a towel over his leg so he couldn't see the damage that was done, because if he seen the damage it would've sent him into shock," Mr Pollock said.
"I've never seen anything like that before, and hopefully never have to again. But I guess it's something, like an image that's going to stick in my mind for a while."
Emergency services arrived quickly and took over from Mr Pollock. The driver was taken to Canberra Hospital, where he underwent emergency surgery. A hospital spokesperson said on Friday morning he was stable.
Mr Pollock and Ms Edwards have lived at the bottom of the Bungendore Road hill for about 18 months, and said it isn't uncommon for people to approach the Yass Road roundabout at speed. "Because of the size of that hill I've always expected something to happen on that hill, but I was expecting it to be from a truck or something because the hill is so long, straight and steep," Mr Pollock said.
"We always hear cars slamming on their brake down that road, but we've never seen an accident quite like that," Ms Edwards said.
"I didn't get a lot of sleep. It was just awful to think about. You start thinking what if it was someone you knew."
Police took the car for mechanical examination, and said the investigation into the crash would continue.