What's up with these "Killer Clown" pranks?

A weird craze that apparently originated in the US, Canada & Australia has now hit these fine isles we call Britannia.
For those unaware, people are dressing up as clowns & I mean scary mother fucker clowns with knives, axes & bats. They wander around when it’s dark & jump out of the shadows frightening the shite out of…& this is the worst of it, mostly young kids.

Our local police even posted a photo on their facebook page showing 2 masks & plastic fake machetes they had confiscated from a couple of 12yr olds who had “pranked” kids in a primary school.
Wondered if anyone here had experienced this first hand & if this dumb trend had occurred where you live, how long did it go on for?