Here's the story.
Elisha tells the Israelites that God will deliver the Moabites into their hand.
The LORD ... will deliver the Moabites ... into your hand. 2 Kings 3.18And when he does, God wants the Israelites to chop down the trees, ruin the wells, and destroy the land.
Ye shall smite every fenced city, and every choice city, and shall fell every good tree, and stop all wells of water, and mar every good piece of land with stones. 3.19So the Israelites kill the Moabites, their trees and crops, and ruin their cities and wells.
The Israelites rose up and smote the Moabites, so that they fled before them: but they went forward smiting the Moabites ... And they beat down the cities, and on every good piece of land cast every man his stone, and filled it; and they stopped all the wells of water, and felled all the good trees. 3.24-25Finally, the Moabite king sacrificed his son as a burnt offering in a desperate attempt to stop the massacre. And it seemed to work, too, since the Israelites stopped killing after that.
Then he took his eldest son that should have reigned in his stead, and offered him for a burnt offering upon the wall. And there was great indignation against Israel: and they departed from him, and returned to their own land. 3.27Since God helped the Israelites smite several Moabite cities, I'll guess 1000 Moabites were killed in five cities, for a total of 5000.
God's next killing: A skeptic is trampled to death