This is not a Darwin award. He is alive.
Many of us carry acetylene bottles in our vehicles, including myself. But like all pressurized cylinders, it must be stored upright. This is especially important for acetylene as it has acetone mixed in to keep the acetylene stable as it likes to go "f this fj" at pressures above 15psig. (see above photo).
What makes me mad about things like this? Did this guy have any sort of warning placard on his vehicle letting others know there was both flammable and compressed gas cylinders within the vehicle? Had this have been a car accident, how would anybody know there was a potential bomb in the back? Obviously no way to tell now, but I highly doubt it.