in parts of the world people have trained baboons and other primates to kill people with automatic weapons.
As far as Virginia possums they r easy to catch,just grab em behind the head.
Any black squirrels in the United States are melanistic,this generally occurs in areas where there is a small gene pool often caused by uncontrolled hunting at one point or habitat fragmentation,this sort of inbreeding can also cause the squirrels or other animals to become aggressive,these animals are more likely to spread and contract diseases.