A group of teen monkey bike riders was seen “really flogging it” and doing “monos” in the moments before one of them crashed into young mother on a zebra crossing, killing her, a court has heard.

Police allege Andrea Lehane was thrown about seven metres when she was hit by mini-motorbike, known as a “monkey bike”, outside Carrum Downs shopping centre about 5.10pm on September 23 last year.

The 34-year-old mother of two suffered critical head injuries. Her family decided to turn off her life support two days later. Caleb Jakobsson, 19, was allegedly riding the monkey bike that hit Ms Lehane.

He is charged with culpable driving and other offences including failing to stop after an accident and unlicensed driving.

Witnesses told Melbourne Magistrates Court on Monday they saw a rider on one wheel, as he overtook a car at the zebra crossing. That rider passed on the right side of the car, before three other riders passed on the left side of the car. One of those riders also pulled a “mono”, the court heard.

Police allege Mr Jakobsson was one of the three riders on the left of the car and had a passenger at the time.

Mechanic Michael Ryan told police the riders were “really flogging it” when they passed him while he was standing outside his workplace about 10 minutes before the crash and estimated they were travelling at 50km/h. He told his boss of concerns there would be an accident.

Asked in court if the riders could have been going slower, he said: “Possible, but not by a significant margin.”

Another witness, Glenn Edgerton, said he saw the riders as they approached the zebra crossing.

“They were going quite fast for the area, I believe,” he said.

“The first bike went over the speed hump, the second pulled what I would call a mono”, he said, before they got to the crossing.

The driver of the car at the crossing, Terence Parata, said he was stopped when he heard the motorbikes and instantly saw the first of the group “popping a mono” outside his right window.

By the time he turned to face the front, he said, the other three riders had gone through and Ms Lehane had been hit.

Mr Parata said it looked as if the first motorbike had clipped Ms Lehane and spun her into the riders on the left.

He said he got out of his car and went to Ms Lehane, who was lying on the ground bleeding.

“My focus was on getting to the lady first. Once I realised there were other people around ringing the police, that’s when the other guy and I gave chase,” he said.

The court heard Mr Parata yelled at the riders, who had slowed and were looking back.

He and another man then got in Mr Parata’s car and pursued the group, but lost them.

Police allege Mr Jakobsson and his passenger were thrown from their bike in the crash, but got back on and rode away.

Pedestrian Monique Eddy said she heard one of the riders say “Oh s–t” after the crash.

Ms Eddy said she closed her eyes when she realised Mr Jakobsson was not going to stop at the crossing, so she did not witness a crash.

She administered first aid when she realised Ms Lehane had been seriously hurt.

Mr Jakobsson is yet to enter a plea. The hearing, which will determine whether he stands trial, continues.

The other riders have appeared before children’s courts.