It takes a special kind of murderer to get himself completely covered in the blood of his victims, especially when his victims are entire families.
He must just hack his way through the town, severing arteries left and right. It must give him a thrill.
Perhaps bathing in your enemies’ blood is a part of the ritual of war for this guy. So much so that with the right heat and humidity, that blood bakes into a new kind of armor, hardening like clay on his skin to help protect him from the next wave of murder ahead of him.