A car mechanic told Downpatrick Crown Court on Wednesday he had been taking a car on a test run and had pulled into the car park at the Somme Heritage Centre.
He said that as he checked the car's diagnostic computer, he noticed a Mark 4 or 5 Volkswagen Golf parked nearby.
However, he said he did not see anyone in or around the 2001-2002 car.
He said that when he later returned to the site, police had the Somme Centre cordoned off.
A man living nearby said shortly after lunchtime, he heard a large bang and saw smoke coming from the car park.
He said when he went to investigate he saw a burning Honda Civic which he photographed on his mobile phone.
The prosecution say the Golf car belonged to 37-year-old Peter Greer who has given his address, as Sherwood Road, Bangor, and that the burning Honda, was the gunmen's getaway car which had been stolen in a creeper burglary in west Belfast two months earlier.
They further claim that when police later arrested Greer's 34-year-old co-accused Jamie Alexander Smith driving the Golf, they found a key to the gunmen's burnt-out Civic under his seat.
Both Smith, who gave his address as Doagh Road, Newtownabbey, and Greer deny the murder of 56-year-old Duncan 'Duggie' Morrison who was blasted to death on May 13 2011, in a flat in Hazelbrook Avenue in the Co Down seaside town.
Smith and Greer, who both had addresses in Belfast at the time, also deny attempting to murder his friend Stephen Norman Ritchie, and possession of the single-barrelled sawn-off shotgun and 9mm pistol used in the double shooting.
Trial Judge David Smyth QC and the jury of seven men and five women have also heard that the day before the "carefully planned and organised killing" Smith and Greer made a "dry-run" to Bangor in his car.
The prosecution further claim that later Greer picked Smith up from his then St Anne's Square home in the centre of Belfast, returning to Greer's Mountcollyer Avenue home in the north of the city.
The two men were then allegedly captured on a CCTV surveillance camera leaving his home and while he is seen getting into his Volkswagen, Smith was allegedly pictured putting a red holdall in the boot of the Honda before travelling "in convoy" to Newtownards.
On the day of the shooting the Volkswagen was again captured on various surveillance cameras, according to the prosecution, driving into the centre of Belfast and then to Newtownards.
Afterwards it was spotted on camera, before it was finally stopped on the Ormeau Road in south Belfast, when Smith was arrested.
The hearing continues.