Kids are doing the Kapa O Pango throat slitting gesture and people are worried.
Isn't this just the same as when we played 'war' as kids?
Let me remember the rules...
You fashioned anything remotely gun looking out of a stick and proceeded to chase your friends round the house making 'e e e e e e!' machine gun noises while pointing stick at said friends.
When is was decided that you'd been 'shot' you were required to 'die' realistically, which involved biffing yourself in a ragdoll fashion onto the lawn or into a hedge. The child who had been shot was then required to count to 20 before getting up and resuming chase.
Sometimes there were disagreements on whether you had been shot or not and the argument went thus:
"I shot you!"
"No you didn't."
Yes I did, when you came round the corner."
"No, you missed!"
In our game we also had grenades. Grenades could be anything from a crab apple to a pine cone and when hurled within a metre or so of a mate meant you had to count to 50 before getting up. Presumable a grenade did more damage so you counted higher to give the kid who got you more or a chance to get away and hide again.
That's how kids, particularly boys played.
As for the child who used the throat slitting gesture to tell his little brother to back off during a disagreement over DVDs, my wife tells a story of a song she and her friends used to sing to her little brother about him being for sale to make him cry.
He's now a strapping man of 22, around 6" 4' in height with a University education, an excellent career ahead of him, steady girlfriend and making his way in the world pretty well.
Let kids be kids. If you wrap 'em in cotton wool for the entirety of their childood, they'll be bugger all use as adults.