It was probably a firecracker, like the ones we get every year on the reservations. Then there is photographic flash powder, which we bought in quantity for use in stage effects. Confine it even slightly and the high-speed stuff goes "bang". We'd set that stuff off in our alley downtown, right next to the police department building wall, frequently in testing our flash pot arrangements.

Then again the I-205 caper could have been a black powder gun firing a blank charge.

The main thing we need to keep in mind is that the best thing to do in these situations is freak out and go into an irrational and pointless frenzy.