They come at night by Garry E. Lewis

When a black hole appears outside of the town of Bluff Springs Missouri, something evil enters into their time zone, something strange, mystery beast begin stalking the local farms slaughtering the livestock, as the local farmers come forward searching for answers, the local town sheriff is lost and confused concerning what these creatures could be, and seeks answers regarding the strange series of events taking place outside of his town. He soon seeks the help of some college professors to help solve this mystery, brought on by this black hole. Where did these creatures come from and how can they be stopped.