Probably someone out on a demo with a car from a dealer (or they work for a dealer). I saw a Camaro at a car lot up here with big bold "426 HP" decals on the door. It's not uncommon for dealers to market cars like this to get attention when people drive by. So before you go throwing stones you might want to gain a bit more knowledge surrounding the circumstance.
Here's a couple examples to give you an idea of the concept:
