A thought experiment: An unknown person calls my house and says that someone is coming over now, and that the person has a gun. I get my own gun, and crouch over my porch railing, ready. A person walks down the street towards my house. Some 20 yards from my porch he reaches towards his pocket. I shoot him dead, thinking he might have a gun. In reality he was gonna check Facebook on his phone, and was in fact not even going to me at all.
Would I be put on trial in this case? Or is this obvious self defense? Would the person who made call be put on trial for manslaughter?