They weren’t just asking him to stop, they were trying to make him stop.
“Travis McMichael drove down Satilla Drive toward the intersection of Buford Road, the report said. They spotted Arbery running down Buford Road. Travis drove down Burford Road and tried unsuccessfully to cut off Arbery’s escape with the truck, the report said.
The Brunswick man then turned and started “running back in the direction from which he came,” the report said. Travis McMichael again tried without success to cut Arbery off with the truck.”
They were pretty careful not to physically touch him, hit him, grab him, or otherwise impede him.
They certainly wanted to make him stop, but it does not appear it ever got physical.
It appears, he did a pretty good job of portraying a guilty person attempting to flee, which can also look a lot like a scared person trying to flee. The difference is in his mind, and he is dead.
They had plenty of opportunities to point guns at him or threaten him, but it does not look as if they ever did so before he attacked the son who had the shotgun.