ON OCTOBER 8, 2015, OUR FAMILY WAS DRIVING ON I-85 NEAR HUNTERSVILLE, NC. WE WERE IN OUR 2015 GMC ACADIA, WHICH WE'D BOUGHT NEW IN AUGUST. WE WERE IN STEADY, MOVING TRAFFIC. THE CABIN WAS QUIET; I WAS DRIVING, MY WIFE WAS IN THE PASSENGER SEAT, AND OUR TWO CHILDREN (AGES 9 AND 7) WERE IN THE SECOND ROW CAPTAIN'S CHAIRS. BOTH CHILDREN WERE WATCHING THEIR IPADS. SUDDENLY WE HEARD WHAT SOUNDED LIKE A PISTOL BEING FIRED INSIDE THE CABIN, FOLLOWED INSTANTLY BY OUR 7 YR OLD SON ('SON') SCREAMING AND YELLING, 'IT HURTS, IT HURTS.' MY WIFE AND I BOTH TURNED AROUND AND SAW SON CLUTCHING HIS LOWER BACK. I NEGOTIATED THE CAR TO THE SHOULDER AND SAW THAT THE ENTIRE HOUSING/CASING OF HIS SEATBELT BUCKLE HAD SPONTANEOUSLY EXPLODED. THE BUCKLE WOULDN'T UNLATCH, BUT MY WIFE GOT HIM OUT OF THE SEAT AND EXAMINED HIM. HE HAD A PUNCTURE/GASH IN HIS LOWER BACK, WHERE SOME OF THE SHRAPNEL HAD HIT HIM. WE FOUND BOTH PLASTIC AND METAL SHARDS IN THE CAR. TO GIVE YOU AN IDEA OF THE FORCE THE EXPLOSION CAUSED, THERE WAS ALSO A 2-4 INCH HOLE IN THE INTERIOR DOOR'S PANELING. ONLINE RESEARCH SUGGESTS THAT A PRETENSIONER MAY HAVE MALFUNCTIONED; A GMC SERVICE MANAGER STATED THAT THE SECOND-ROW CAPTAIN CHAIR SHOULD NOT HAVE A PRETENSIONER.