Hell hounds, does anyone know what this means?

This Is Starting To Scare Me,
OK, My Moms Dog Died A Few Weeks Back.
And Since Then, I'm Having These Dreams Of Him Coming Back As A Hell hound. Everynight Too,And He's Trying To Kill My Family, And Now...
I'm Starting To See Him When I'm Not Sleeping...

...
Does Anyone Know What That Means?

In mythology hell hounds are a demonic dogs of hell. Hell hounds typically have features such as an unnaturally large size, a black fur color, glowing eyes, super strength or speed, ghostly or phantom characteristics, and sometimes even the ability to talk. They are often assigned to guard the entrance to the world of the dead or undertake other duties related to the afterlife or the supernatural, such as hunting down lost souls or guarding a supernatural treasure.
source: http://en.wikipedia.org/wiki/Hellhound

In regards to seeing a hell hound, I guess its all depends on what you believe. If you don't believe in hell hounds then it could just be your mind playing tricks on you. You should probably talk to someone who knows about this subject, they can help you more.