We had the 2006 Suburban parked with the engine running while our family was just starting to get in. A couple of them noticed a slight smoke smell which we followed and we trailed it to the rear of the vehicle. While I was pulling off a left rear column trim piece to locate where the smoke was coming from, the far rear dome light fixture started dripping melted and burning plastic close by my head. I looked up and saw the rear dome light fixture on fire and flicked it down into the rear cargo area. One of the family was already fetching a fire extinguisher and as they arrived I used it to put out what fire was left in the headliner.