FWIW, the patter was probably ash and debris from the fireworks. Bits of cardboard from the tubes, that sort of thing. I actually had some of that land on me once (thank goodness it was not burning at the time) and it's more substantial than most people seem to realize. Of course, it depends on how close the fireworks were to you and if the wind was blowing your way (or if they were launching at an angle slightly towards you).
(no subject)