Friendly Fire: God forced "a great multitude" to kill each other

"A great multitude" of Ammonites, Moabites, and Edomites gathered to attack the kingdom of Judah.

There cometh a great multitude against thee from beyond the sea ... the children of Ammon and Moab and mount Seir [the Edomites]. 2 Chronicles 20.2

The king of Judah, Jehoshaphat, prays and prays and prays some more, asking God for help.

And Jehoshaphat stood in the congregation of Judah ... And said, O LORD God of our fathers, art not thou God in heaven? and rulest not thou over all the kingdoms of the heathen? and in thine hand is there not power and might, so that none is able to withstand thee?
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And now, behold, the children of Ammon and Moab and mount Seir ... invade.
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O our God, wilt thou not judge them? for we have no might against this great company that cometh against us; neither know we what to do: but our eyes are upon thee. 20.5-12

Everyone in Judah heard Jehoshaphat's boring prayer.

All Judah stood before the LORD, with their little ones, their wives, and their children. 20.13

And then the spirit of the Lord came upon Jahaziel (the son of Zechariah, the son of Benaiah, the son of Jeiel, the son of Mattaniah, a Levite of the sons of Asaph) who told the people of Judah not to worry. They didn’t even need to fight; God would fight for them.

Then upon Jahaziel the son of Zechariah, the son of Benaiah, the son of Jeiel, the son of Mattaniah, a Levite of the sons of Asaph, came the Spirit of the LORD in the midst of the congregation; And he said, Hearken ye, all Judah, and ye inhabitants of Jerusalem, and thou king Jehoshaphat, Thus saith the LORD unto you, Be not afraid nor dismayed by reason of this great multitude; for the battle is not yours, but God's. ... Ye shall not need to fight in this battle. 20.14-17

Then Jehoshaphat and the entire population of Judah fell on their faces.

Jehoshaphat bowed his head with his face to the ground: and all Judah and the inhabitants of Jerusalem fell before the LORD, worshipping the LORD. 20.18

Jehoshaphat appointed singers to praise the beauty and holiness and say to the army, "Praise the Lord."

Jehoshaphat ... appointed singers unto the LORD, and that should praise the beauty of holiness, as they went out before the army, and to say, Praise the LORD. 20.20-21

And God took care of everything else.

He ambushed the opposing army, forcing the Ammonites and the Moabites to kill the Edomites, and vice versa until "every one helped to destroy another."

When they began to sing and to praise, the LORD set ambushments against the children of Ammon, Moab, and mount Seir, which were come against Judah; and they were smitten. For the children of Ammon and Moab stood up against the inhabitants of mount Seir, utterly to slay and destroy them: and when they had made an end of the inhabitants of Seir, every one helped to destroy another. 20.22-23

And so when everyone in Judah went up to the watch tower, they saw nothing but dead bodies.

When Judah came toward the watch tower in the wilderness, they looked unto the multitude, and, behold, they were dead bodies fallen to the earth, and none escaped. 20.24

Then the people of Judah came down from the watch tower and stripped all the booty from the dead bodies. It took them three days, but they got lots of cool stuff, including precious jewels. But there was just too much for them to carry away.

When Jehoshaphat and his people came to take away the spoil of them, they found among them in abundance both riches with the dead bodies, and precious jewels, which they stripped off for themselves, more than they could carry away: and they were three days in gathering of the spoil, it was so much. 20.25

(Since there was "a great multitude" of Ammonites, Moabites, and Edomites, I estimated 30,000, 10,000 from each tribe.)

God's next killing: God made Johoram's bowels fall out