A masked man holding a gun approached him at about 10:35 BST in a car park in Glenarm on Sunday and demanded the man's car keys.
He then made off from the car park on New Road in a red Ford Fiesta.
A robbery at a shop on Coast Road in Ballygally in County Antrim was reported about 15 minutes later.
A masked man with a gun entered the premises and left with a sum of cash after demanding money from staff.
The red Ford Fiesta was found abandoned at about 11:15 BST on Dickeystown Road in Glenarm.
Police believe the two robberies could be linked.
No-one was injured in the incidents but both the man whose car was stolen and the shop staff were left "very badly shaken", police said.
Police are appealing for anyone who saw the car to contact them.

On Friday, the Florida jury ruled Gawker had violated Hogan's right to privacy, awarding him $115m (Â£79m) for economic damage and emotional distress.
But jurors decided on the additional measure as a punishment for the company and a deterrent to others.
Gawker, who warned the verdict was already "debilitating", will appeal.
The video was posted in 2012 after Hogan, whose given name is Terry Bollea, was secretly recorded having sex with his friend's wife.
Hogan's legal team successfully argued the New York-based website violated his privacy and the video was not newsworthy.
The closely-watched case raised questions about the freedom of the press in the digital age and could lead to greater caution among online sites.
Gawker Media was hit with a $15m ruling, while owner Nick Denton was stung with an additional $10 million.
The editor who posted the video and wrote the accompanying post, AJ Daulerio, must also pay $100,000.
However correspondents say the company stands a good chance of getting the damages reduced or reversed on appeal.
The jury was told that Gawker Media is worth $83 million, while Nick Denton has a total of $121 million. Mr Daulerio has no assets, the court heard, only thousands of dollars in student debts.

Three years ago, rugby league legend Andy Johnson and his wife Alex received the news that all parents dread - their "cheeky, excitable and a big softy at heart" young son was diagnosed with an incurable condition which will probably claim his life before he turns 30.
They were told Jack has Duchenne's Muscular Dystrophy - a terminal muscle-wasting disease.
Doctors predict their energetic little boy, who is now aged seven, will be in a wheelchair by the age of 12.
Former Wigan Warriors star Johnson, who lives in Wigan with Alex, Jack and his little brother, three-year-old Josh, knows it is a race against time to find a cure.
The couple decided they had to do something to try to push research for a cure.
"A breakthrough is imminent," said Andy, 40, who retired from rugby league in 2005.
With Alex, 30, he set up a charity, Joining Jack, "to help move things forward for Jack and other children like him".
While focussing much of their energies on the charity, Andy admits it is impossible not to cry on a daily basis when thinking about what faces Jack.
"It's like little deaths," he said. "You lose the use of your arms, then your legs."
Nothing short of a cure can make it better, Andy said, but he says the support his family has had from people has been overwhelming.
The charity is now backed by some of the country's biggest sports stars, including Olympic champion and Tour de France winner Sir Bradley Wiggins and dual-code rugby player Sam Burgess.
As for Jack himself, does he know about his condition?
"Jack's aware that something is going on," said Andy. "But not quite what".
You can hear the Tales of the 10 on BBC Radio Manchester each weekday until Friday, 23 January.
A man has been robbed at gunpoint as he was taking photographs in a village on the County Antrim coast.
[NEXT_CONCEPT]
Ex-professional wrestler Hulk Hogan has won a further $25m (Â£17m) in punitive damages from gossip site Gawker over the publication of a sex tape.
[NEXT_CONCEPT]
BBC Radio Manchester is taking a journey across Greater Manchester's 10 boroughs to meet some of the most inspiring people who live in the region.