David said to Abiathar, I knew on that day, when Doeg the Edomite was there, that he would surely tell Saul: I have occasioned [the death] of all the persons of your father's house.
So the one escaped to David from the house of Ahimelech, and David felt really responsible for the death of all of those families. He knew that he made a mistake in letting this Doeg go. He should've killed him. "