They broke the law by trespassing. He should have shot them both before they got a chance to see him. Of course he didn't expect to be shot for exercising his right to defend himself with a firearm.
He could have done it from his window and not even went outside. If he used his head he would have had them and been cleared, because he could have claimed that the two dead mean both threatened him with their guns.
I'm outta here.
You must be kidding.