2 Kings 10:6-9
Then Jehu wrote them a second letter, saying, “If you are on my side and will obey me, take the heads of your master’s sons and come to me in Jezreel by this time tomorrow.”
Now the royal princes, seventy of them, were with the leading men of the city, who were rearing them. 7When the letter arrived, these men took the princes and slaughtered all seventy of them. They put their heads in baskets and sent them to Jehu in Jezreel. 8When the messenger arrived, he told Jehu, “They have brought the heads of the princes.”
Then Jehu ordered, “Put them in two piles at the entrance of the city gate until morning.”
9The next morning Jehu went out. He stood before all the people and said, “You are innocent. It was I who conspired against my master and killed him, but who killed all these?
Jehu knew who killed the 70 sons of Ahab. Why did he ask "who killed all these?" as if he didn't know?