This is pretty common, especially when using petrol/gasoline as the accelerant. There’s two big mistakes people seem to make:

1. they’ll start the fire then pour on the accelerant and the fire will travel back up the stream because it’s not a ghost
2. they don’t realize that the fumes are also flammable, so the fire can easily jump from the pooled accelerant via the evaporating gas to them and the container of more accelerant they’re holding, resulting in an exciting light show if you’re outside of the blast zone