A Murderous Spirit is A Manifestation of Satan

In his commentary on John, Calvin writes

When he says that the devil was a murderer, he means that he contrived the destruction of man; for as soon as man was created, Satan, impelled by a wicked desire of doing injury, bent his strength to destroy him.

All murderous intentions spring from that same satanic desire to destroy the lives of others.  From abortion, to terrorism, to gang violence, to war.  All of it is demonic in that it relishes the death of another and has as its goal the ruination of life.