Has he "seen" anyone since coming home from vacation?
Did he supposedly see this "wolf-man" around the time of sleep / naps / when really tired?
When your child says he is scared of something that might be a spirit, never enter into that negative state. Right away let him know that he is not to be scared. Bring as much positivity to the situation as you can, and since he is so young, you can probably distract him from it right away. Playing into anyone's negativity will only breed negativity and then..anything can happen.
If he has not seen this "wolf-man" or scary person since being home from vacation, I wouldn't worry about it, but I would probably advise against going there for vacation again. I would avoid asking him about it too unless he sees him again.
Maybe ask him if he sees anything else?
Also, because children are so impressionable....he could be just using an active imagination. Maybe he had a bad dream, and its manifesting in his waking mind, into the best way he knows how to describe.
Good luck, and keep it positive when around him!
~Nikki