Weird Stuff Found Under the Carpets in My Son's Car

My son bought a 2009 Suzuki SX4 a few months back.  A few weeks after he bought it, he came to a complete screeching panic stop to avoid an idiot who was not paying attention to little things on the road like other cars.  Shortly thereafter, he noticed an odd sound like pieces of metal or broken glass rolling around.  The dealership from whom he bought it charged him a pile of money but could not find nothing wrong, or even anything that explained the weird noise.

He finally chased down the noise.  Under the front right carpeting, he found what at first he thought were ball bearings.  This is worrisome; where would ball bearings have come out, and what bearings needed them?  But after I looked at them for a while, I realized that they were not ball bearings, because they were not regular enough in shape or finish.  They appear to be steel shot, like might come out of dove loads.  What?

At first I wondered if this was a piece of noisy sabotage put in by an angry Suzuki assembly line worker.  You probably know the story of a clever saboteur on the Cadillac line back in the 1950s who put a piece of masking tape and a washer inside the seat so that once the vehicle was up to freeway speed, it would rattle back and forth, irritating customers who had bought a very expensive car -- and not a rattletrap!  The cost of repair was substantial, because the seats had to be torn apart to remove this cheap piece of sabotage.

Nor does it appear to be the cause of why the car was traded into the dealer.  This noise only appeared many weeks after my son bought the car.  There were weird noises at first.

The problem with this explanation is that this only failed after an extreme braking event, and far after the original factory warranty.  I now have a different theory.  This is Idaho.  I suspect that somehow a shotgun shell slipped out of someone's gun in the trunk area, it managed to end up somewhere under the rear seat, and pressure caused the shotgun shell to rupture.  Under extreme breaking, these hundreds (and I mean literally hundreds) of pellets flew forward into the area under the front passenger seat.

We managed to vacuum nearly all of them out -- or at least so many that they are no longer particularly noisy or disturbing -- but I do wonder where the rest of the shell is.  Some day, this Suzuki is going to be crushed for scrap, and dropped into a melting pot -- and there is going to be a rather loud bang as the primer and powder go off.