Night of the Lepus

Arizona rancher Cole Hillman (Rory Calhoun), dealing with massive rabbit overpopulation on his land, calls on a local college president, Elgin Clark (DeForest Kelley), to help him. In order to humanely resolve the matter, Elgin brings in researchers Roy (Stuart Whitman) and Gerry Bennett (Janet Leigh), who inject the rabbits with chemicals. However, they fail to anticipate the consequences of their actions. A breed of giant mutant rabbits emerges and starts killing every human in sight.