Brush with a Mini Bully

Tell me how this appears to you.. 2 bigger children nudged 1 tiny child under an old table behind school property, away from everyone else. Big Kid 1 is about 10 or 11, Big Kid 2 maybe 9. And Tiny Kid is really small, maybe 7 or 8 (or a 9-year old who's small for his age).

Big Kid 1 is empty-handed. Big Kid 2 is holding a long branch against the table. I stopped the car just outside to the school property and asked Big Kid 1 what they're doing. He said "We're just sitting around..". Tiny Kid started running towards the school canteen, followed by Big Kid 2. Big Kid 1 remained in the same area & was looking at a tree as I drove away.

Questions:
What were they doing there? Just playing or just about to do something sinister?
Why are the Big Kids standing when they're just 'sitting around'?
What happened? Did I just stop 2 bullies from exerting their power?

I left feeling dumbfounded. Bullies are alive and well, in our schools.. on the roads and in the offices (more of this later...).