To me it seems that the 50,000 smitten was either in addition to or including the ones who looked in.
And, if God is real, and is capable of creating life, He is certainly capable of mass destruction.
Though the story doesn't make it into Bible storybooks, I do know many Christians who read straight from the Bible itself to their children (I am one, and I too was read the KJV as a child, even with all of its blood and gore. May be questionable parenting to you, who are most certainly entitled to your opinion, but to me it seemed normal. I also grew up with the understanding that the arrival of Jesus in human form provided for violence toward others in the name of God to become unnecessary and absolutely unacceptable).