Payson Az range mishap

I was volunteering as RSO at our local range when a 45ACP high point carbine faile. One picture shows the blown out barrel and the other a bullet that ended up under the forehead skin of an onlooker. She is fine after a CAT scan and a few stiches. Could have been alot worse. Not sure of the cause, the shooter said no squib, LEO thought maybe an extractor problem or dbl feed. Found the remains of 3 slugs.