I find this highly suspicious. At the same time, and odd and unsure way of killing someone that will attract unwanted attention.
I hadn't thought of the alcohol component before, that explains things a bit.. but I have a hard time seeing it create flames like that. I suppose if the alcohol also ignited the gastank. But what kind of chain of events would cause that to happen?
The only first hand account I read said a woman in the back said something to the driver about smoke, he assumed she was asking about smoking a cigarette, and then there was screaming to stop the car and the flames erupted. I guess we will hear more in the coming days about where the initial smoke came from.