Albert Barnes Commentary 1 Samuel 22:18

"And the king said to Doeg, Turn thou, and fall upon the priests. And Doeg the Edomite turned, and he fell upon the priests, and he slew on that day fourscore and five persons that did wear a linen ephod." — 1 Samuel 22:18 (ASV)

We are not to suppose that Doeg killed them all with his own hand. He had a band of men under his command, many or all of whom were perhaps foreigners like himself, and very likely of a Bedouin tribe, to whom bloodshed was quite natural and the priests of the Lord were of no more account than so many sheep or oxen.