The gunmen who killed Malcolm McKeown in Down County last month waited nearly an hour at the gas station, police said.
In the new CCTV footage, a dark blue VW Passat car is being seen at Dewart's gas station in Waringstown at 18:23 BST on 19 August.
The car left the gas station 56 minutes later.
The 54-year-old was found dead in his silver BMW behind Dewart's shortly before 9:00 pm BST.
Mr. McKeown had been shot six times.
The VW Passat was later found burned on Glenavon Lane in Lurgan.
Detective detective Peter Montgomery has asked for witnesses to appear.
"There were football practices and trials going on nearby, so some parents might witness the Passat fire," he said.
"It was a frightening murder committed at close range in broad daylight Mr. McKeown was the father of three children and his family deserved justice."
He also repeated a call for information on another car, a gray VW Golf, which had been seen in the Greenhill Park area on the day of the murder.
Police believe the murder is linked to a "long-standing quarrel".