An Aztec
Hmm ... no post-crash fire??
I've got over 1,000hrs on an Aztec; a difficult aircraft to get into trouble with. I wonder whether in a rush to depart he may have mishandled fuel selectors instead of cowl flaps (not impossible to do if you're not paying attention .. I've seen it done on my own aircraft by a guy who steadfastly refused to use a check list).
All the same; rotten luck.