I have an evil dog please help me?

Ok so not to long ago i was given a beatiful black lab for my birthday, well it turns out it is evil. We have a huge property where tons of little animals such as squirrels, ducks, and bunnies and other orted critters would run free. Well it turns out she managed to kill all of them... I kid you not i found a beheaded dove sitting in my porch. Also whenever we are around she is usually very nice, but when shes alone she tries to kill peoplenot by biting them but in strange ways like Last week the directv man came by to fix our dish. It turns out something mysteriously knocked his ladder down and the poor man was stuck up there for over 2 hours... We have sound proof windows so we couldnt hear him lol. Im scared if i get rid of it it will return and kill me while i sleep... I started calling it the black death.. Any advice?