Yea can be a slippery slope
Copied and pasted from the AG ORM:
Defense of Others A person may defend another only if the protected person would have had the right to use deadly force in self-defense himself. Under Ohio law, a person may defend family members, friends, or strangers. However, just as if he were protecting himself, a person cannot use any more force than is reasonable and necessary to prevent the harm threatened. A defendant who claims he used deadly force to protect another has to prove that he reasonably and honestly believed that the person he protected was in immediate danger of serious bodily harm or death and that deadly force was the only way to protect the person from that danger. Furthermore, the defendant also must show that the protected person was not at fault for creating the situation and did not have a duty to leave or avoid the situation. WARNING: The law specifically discourages citizens from taking matters into their own hands and acting as law enforcement. This is true even if you think you are performing a good deed by protecting someone or helping law enforcement. The Ohio Supreme Court has ruled that a person risks criminal charges if he interferes in a struggle and protects the person who was at fault, even if he mistakenly believed that person did not create the situation. In other words, if you misinterpret a situation and interfere, you may face criminal charges because your use of deadly force is not justified. If you do not know all the facts and interfere, you will not be justified to use force. It does not matter that you mistakenly believed another was in danger and not at fault.