The road was covered with center-fire cartridges. Mostly 9mm, but with a sprinkling of 7.62x39 thrown in for good measure. It seemed odd, but at the time, I wrote it off as maybe someone had dropped a bucket of range pickings off the back of their pickup truck. As we drove on, we heard a mass of sirens approaching.
Here it may be worth your time to see if there is a scanner club or like organization in your area to check with. Ham radio clubs often (but not always) have members knowledgeable on the local communications 'scene'. It doesn't hurt to ask.