Deuteronomy 21:6-9

6Then all the elders of the city nearest the victim shall wash their hands by the stream over the heifer whose neck has been broken, 7and they shall declare, “Our hands did not shed this blood, nor did our eyes see it. 8Accept this atonement, O LORD, for Your people Israel whom You have redeemed, and do not hold the shedding of innocent blood against them.”

And the bloodshed will be atoned for. 9So you shall purge from among you the guilt of shedding innocent blood, since you have done what is right in the eyes of the LORD.