take him a cup of scalding hot coffee and just when he's holding it, have someone drive off, and shout "hey, gogogo, he's getting away" and watch him try NOT to get the coffee someplace it would REALLY hurt - and if it DOES... it's HIS fault, HE dropped it
OR
go up to him, hand him the dog's leesh and tell him can just as well keep an eye on Blacky as well, since he's there anyway - then walk off as fast as you can. It helps if Blacky is a mean doberman.