Guys... I've moved the off topic drift to the OT area, you can carry on the discussion on Police rights and behaviour here:
With respect to the intent of the OP, I had a (much milder) encounter when my son was in elementary school, I was unexpectedly off work one day and decided to surprise him by picking him up at school... not thinking, I kind of 'hid' behind a tree near where his bicycle was locked. Another parent waiting for a child more or less accosted me want to know why I was lurking at a schoolyard.
Initially I was offended, insulted, etc.. but later came to realize that that was a good thing and I'd been behaving like someone might with baser motives that I'd had... ultimately I had to be grateful for the vigilance.
Certainly nothing like the ordeal the OP was put through, of course......