It probably isn't a big deal.
Phobia of clowns seem a bit irrational to me but phobias are, I suppose, by definition irrational. Just remember it's just a person underneath all that makeup.
As for the clown, sure, it could be the next John Wayne Gacy but I suspects it's more likely to be some high school or college kid who thinks it would be hilarious to freak the neighbors out. Who know, maybe he might even gain some notoriety from the local news talking about him.