It sounds like a refueling incident, where there fumes accumulated and then were ignighted. Perhaps not running a blower, not keeping all cabin doors and windows shut when refusing??? Or non ignition protected equipment in the bilge area where gasoline vapors accumulate.
When I owned inboard gas boats, I always had a "fume detector" in the bilge. Closed all compartments, after fueling ran the blower for 5 minutes, and personally checked the bilge before turning on any electric item or starting the engine.
When I was 11 years old, and the night before the first TransPac race after WWII. about 70' "Sea Hawk" was owned by one of the Hollywood stars, and his wife lit a cigarette, and a bilge full of propane exploded and the yacht burned to the waterline. I was aboard my dad's boat about 100' away...I have seen at least 4 boats explode and burn from gasoline sources and another 3 or 4 from Propane. Its serious business!