I would do what I do normally do when I'm alone and I get scared. Grab my phone, a butcher knife, my cat and my iPod. Then I'd hide in the closet with the closet light on and play on my iPod till I feel sleepy.
I would be really scared, and probably start crying. But if i were home alone for a long period of time, especially at night, i would always have a knife with me. So then, i guess i would laugh a little, because the serial killer just blew his cover. And plus, i would have the knife, he'd never know what was coming.
When I'm home alone I always have my gun with me so I would probably chamber a round and scare the crap out of whoever farted it is a 12 gauge pump shotgun that I always have loaded and beside my bed. So if your going to try to sneak up on me while I'm alone don't fart or you will probably die