He explained he had just turned into Lower Domain Drive and was heading up the hill in his car to go to a football match when the joggers flagged him down.
"They were a bit frantic - one of them was just blocking the road," the witness said.
"It was a shock to hear something like this had happened, especially in such a populated area."
The car driver said there were no obvious signs around Mason's body to indicate what had happened.
The joggers had found a backpack nearby with food in it.
The area is a well known spot for rough sleepers.
Police said today inquiries into Mason's death were ongoing.