What's happening here?

The other day there were these two boys (They looked to be about 7 and 9 years old) in line behind me in the bank. At first they were standing calmly beside a man that I assume was their father. As the long line slowly crept forward, the boys became impatient and began goofing around. At first they appeared to be playing tag, then they split up and played alone for a few minutes. All of this seemed very normal. Boys will be boys after all. Then after a few more minutes they were back playing with one another.

What happened next shocked me... The older boy all of a sudden spotted a surveillance camera in a corner of the bank. He nudged the smaller boy, and without a word spoken between them, both raised their little hands as if they were holding shotguns and pretended to fire at the camera. Next, the smaller boy aimed his "gun" at one of the tellers and proceeded to pretend to shoot her. They both continued their "massacre" until after about a minute, when their father finally told them to stop.

I stood there for a moment, absorbing what I had just witnessed. I was actually shaking, thinking about the fact that this was just normal play to these kids. Nothing out of the ordinary. Is this really the way that we are allowing our children to play? I was really disturbed by what I saw that day... I think the image will haunt me for a long time...