To shoot the messenger means to blame a person who has told them bad news instead of blaming the person who is responsible for the situation.
Consider the staetement "I knew this whole situation wasn't his fault, and it wasn't right for me to yell at him for something that wasn't his doing.". Based on this statement, is "I knew this whole situation wasn't his fault, and it wasn't right for me to shoot the messenger." a true statement? Yes/no/unknown