Keep your eye on the top right of the screen.
In the footage, the man can just about be seen on top of the vehicle, to the right, where it is believed he is trying to put diesel into a canister strapped onto the roof of his van.
Because it is difficult to see, he takes out a lighter which ignites the fumes causing a mini explosion, and burning flames begin flowing out of the nozzle.
The panicked man then drops the nozzle, which sprays burning fuel over the forecourt and other vehicles as he tries to flee for safety