Filled and slightly pressurized ball with flammable gas + oxygen/air mixture. The water cooled the ball causing the pressure to drop which allowed the flame to enter the ball causing boom.

Mistake was filling ball with fuel + oxygen… pure fuel wouldn’t have created that nice of a flame but wouldn’t have been able to explode like that.

Source: I was a kid who had unsupervised access to a welding shop while growing up. Oxy-acetylene makes one hell of a bang

Haha but you included more info. Did you know it or find it? I saw the word Bishop twice in the photo. Googled it. Found the airport. Flipped through street view photos and found the baggage claim.

Eastern Sierra Regional Airport in Bishop California

Ahh yes, the bury your head in the sand trick