First graders think that to kill someone, simply means that they won't see that person ever again.  Or that they are "Sending them to be with Jesus".  Their greatest worry for "killing" anyone, would be that they may get on Santa's "bad" list.  In their childish world view, they have not yet grasped what death really is.  How often are children told that "Grandma is in heaven with Jesus, watching over us."  In my day, we played "Cowboys and Indians" all the time, and we "killed"each other all day long.  Get a grip people!