Jareth could have likely avoided the bullet, as he had avoided all sorts of other dangers in Los Angeles before, had he not been fixated on the boy.
Toby Once he knew who the child was, all sorts of things stood out that hadn't before, small familial resemblances to Sarah, the fact that he was with a known supporter of Sarah and THE WITCH. His mind was whirling with possibilities and plans. Perhaps if he took Toby back to the Labyrinth, Sarah would follow him and then things would be different. If only he had known that her little brother was here long ago things would have been different. Jareth could have stood a chance against the Scarboy if only he had had the very child that Sarah wished away there under his wing. If only this encounter had occured months ago Sarah might already be his.
If only.
He didn't feel the bullet when it hit his head, it was just too fast. There was no pain, just a moment when the scheming and planning stopped and the Goblin King fell dead toward the pavement. There wasn't even enough time for the dangerous look on his face to morph into something else, like fear or surprise.
Jareth's time was up.
He hit the concrete, his absurd hair and clothing making him look more like an actor in some comic reenactment of a tragedy than a dead man, and then, before blood could even begin to flow (if indeed the great Goblin King had such mortal things as a heart or blood) he simply vanished.