“Murderous” by what standard? There’s the legal standard and the moral standard.
Also, if a parent walks in on someone molesting their child, chases that fleeing someone down and kills them in hot blood, that may be murder but mercy might be in order.
On the other hand, if someone kills another in cold blood to eliminate them as a witness to something or the other, mercy probably is not in order.
Just goes to show how even the taking of a life is relative, but for some reason, people don’t like to hear about relativism.