Monash University graduate and part-time tutor, Ben van Mierlo, 21, had driven to Southland shopping centre in Cheltenham to pick up his husband, Jay, from work.

Mr van Mierlo was chatting on the phone to his mother Roslyn about borrowing the family tent for a camping trip he was planning as he drove his Toyota Yaris into the shopping centre car park about 1.25pm and pulled into a vacant bay.

"I don't even remember if I turned the car off. I had seriously just got into the park," Mr van Mierlo said.

"As soon as the car stopped, the driver's door opened, I thought it was Jay ...and then I looked up and I saw this guy in a really puffy jacket, really dark colour.

"He yelled and screamed at me to 'get out of the car, get out of the car'.

Mr van Mierlo said the man, who was about 180 centimetres tall and well-built, had an olive complexion, though most of his face was hidden by the jacket's hood, which was pulled tight around the man's face. The man was also wearing sunglasses.

"I hesitated, so he grabbed my shirt and pulled me out of the car," Mr van Mierlo said.

"Then he jumped in the driver's seat. I am yelling and screaming at him, 'what are you doing? Stop! Help, someone!'

"And I see two guys come out from this car parked behind me that I hadn't noticed at all, and they came out, opened the door of my car, they are all now sitting in my car. And they are yelling, 'go, go'."

Mr van Mierlo said the driver quickly reversed the car and then drove straight off. The men left behind a white Toyota Hilux ute that police allege was stolen from Dingley Village, in Melbourne's south-east in the morning.

"I was pretty shocked ...really freaked out," Mr van Mierlo said.

"I ran out ...yelling out after the car, 'that's my car, that's my car, someone help'."

He said bystanders rushed to help him and waited with him until police arrived. One also helped him call his mother, who had been left fearing the worst when her phone conversation with her youngest son was abruptly cut off.

"We were still just finishing off, then all of a sudden I heard, 'get out of the car, get out of the car', 'no, no', and just a whole lot of noise and 'beep, beep'," she said.

"And I am listening to all of this, I am going 'what's going on? Ben? Ben?'

"And all of a sudden the phone just cut off."

"All I could think of was, 'okay, I didn't hear a bang. So, he didn't run into anything, and no one ran into him."

Ms van Mierlo said all she wanted now was to see the culprits caught and taken off the streets so no one else would have to go through the same experience.

Victoria Police spokeswoman Belinda Batty said Kingston crime investigation unit detectives were appealing for public assistance following two car thefts on Monday.

Ms Batty said after the carjacking,  it was believed the offenders stole a set of number plates, 1CE 6TU, nearby and continued driving.

To compound his loss, Mr van Mierlo also had his prescription glasses and phone, as well as his and his husband Jay's wallet in the car. Jay's wallet was later handed in to Caulfield police station.

But, he considered himself lucky to have escaped unharmed.

"So many of these have ended in injuries or worse.  I have got not a scratch on me," Mr van Mierlo said.

"I am a little shaken up, a little scared ...but I am fine."

Mr van Mierlo said he wanted to thank the people who helped him after the incident.

"They were all so kind," he said.

"One of the guys, who gave me his phone to dial, was from Northcote, probably rather busy, but he hung around with me the whole time. He offered to drive me home. Just really waited until the police said they were going to help me."

A woman ran inside to call security and then ran back to tell Mr van Mierlo's husband about the incident.

Mr van Mierlo said he still could not believe the thieves would dare to strike in the middle of the day at such a public venue.

"If it happens to you in the middle of Southland shopping centre, at 1.30 in the afternoon, I don't know where anyone is safe."

Anyone with any information is urged to contact Crime Stoppers on 1800 333 000 or submit a confidential crime report to www.crimestoppersvic.com.au

with Broede Carmody