It has all the characteristics of an accidental gas explosion from an RV with either a leak or something accidentally or possibly deliberate, but most likely an accident. The voice alarm is a better idea than a siren like my RV has, which nobody would know what it means. The voice alarm should be more informative. If the RV was parked in the evening and maybe it was cold so they left the furnace on OR often people will turn a stove burner on. Now maybe that is what happened and the flame went out so the RV filled with gas, at first the inside alarm would sound like a smoke detector. But when gas concentration becomes critical explosion risk then the siren or voice announce alarm comes on.