How so? By every definition, the home owner is the one who is creating the imminent threat and since they did not go on his property, he has no right to hold them at gun point. I'm not saying the two teenagers should run him over, and if there were another route that he was not blocking, go that way, but they should do what ever they need to, to escape and if he were blocking the only way to escape, then I don't blame him.
Not to mention, according to the article, he fired shots after the car had already passed him, thus the what ever danger he faced, had already passed. He should most definitely be charged.