There would have been a big crowd in the street right at closing, most likely
It would have been an even bigger massacre if they had managed to ram the car into the nightclub before setting it off. A gasoline/propane explosion inside a confined space would have probably killed most of the people there
http://news.sky.com/skynews/article/0,,70131-1272910,00.html
The massive quantity of petrol along with several propane gas cylinders could have combined to create a massive explosion.
There was so much petrol in the vehicle that the highly flammable vapour it gave off is believed to have looked like smoke.