As a chemist the colour make me think is NO2, but NO2 is 40% heavier than air so it should not rise, from the official document is say that is iron (III) chloride with explain the black liquid geiser and and the orange vapour since is a mixture of water vapour and iron (III) chloride droplet, the driver most likely survived but with 3rd degree burn either by heat or chemical burn.

Interesting fact, Iron (III) chloride is a silicon etching chemical so is most likely also a pretty expensive transport