Gunman
Not me but my mate, several years ago:

There was a bunch of friends all gone away to Belper for a week or so in a big house. Around 16 lads and lasses all fairly well behaved and in favour of a drink or two. It was just a nice holiday away with plenty bbq's and hi-jinx in the Derbyshire sunshine.

On a fairly routine drive through town for supplies; "G" at a set of traffic lights pointed a cap gun out of the window at an elderly lady and gave the "pew pew" motion, before the car set off again.

A nice afternoon was had by all until a very worrying phonecall came through from "B's" parents back up north. They'd had a phonecall from the Derbyshire police who were in the process of hunting a gunman that had been shooting at members of the public. "B's" reg plate had been sighted so they called the number it was registered to.

Quite a large amount of resources had been employed to find this vehicle and very real threat to the public; helicopter, squad cars, traffic surveillance, the lot.

A nice bbq turned into everyone sat in the main room of the house, on the receiving end of an industrial scale bollocking off a few very very angry police officers. Should have been arrested? It would have been much funnier if they'd been found while driving through town!
(Monkeystrumpet monkey. Monkey, MONKEY!!!, Tue 31 Jan 2012, 15:04, 2 replies)

Deservedly so
What a stupid thing to do.

I once had a replica full-sized gun lighter. It was made entirely of metal and on the whole completely realistic, the sort of thing you probably can't buy anymore. My brother took it with him to school one day to show his mates without asking me. He had to explain to me later that evening that they were walking down the street in broad daylight while 'playing' with it and predictably the armed police turned up before very long following a tip-off from a concerned member of the public. They were all allowed to go home following a slight telling off but I never saw my lighter again.
(TheManWithThePlan cussed your mum on, Tue 31 Jan 2012, 15:27, closed)

My neighbour's boy had an armed response team descend upon him
as he and his friend were pretending to stab one another with a plastic knife from a Batman playset.
Over the top, perhaps, but not unexpected, given that a copper had been stabbed to death in town the previous week.
( monster munch person, man, woman... camera... TV?, Tue 31 Jan 2012, 19:11, closed)