Trying to unsuccessfully light up a gas stove. Relighting appliances, if you don't know what you're doing, is very dangerous. It looked like the stove attempted to relight during the cooking cycle or didn't start in the first place, leading the gas to build up to the lel (lower explosive limit). The gas valve normally would shut off flow, but it didn't work for some reason. Gas is very trustworthy, it will do that everytime if you have malfunctioning stuff or override safety features. They very well could have had work done or the gas shutoff, and then didn't let the gas company relight their stuff for them. A pocket of air gets in their house piping, blows out the pilot, then floods the closed oven with gas until it's accidentally lit.