Maybe some idiot shooting tracers, like what happened at the DFW Gun Range?
Pshaw, we’ve shot worse than that.. Tannerite free-for-all.
Could be tracers though, hadn’t thought of that.
But what is there downrange to set on fire?
Back in 1968, in the USAF, we went to the firing range with M1 carbines and tracer ammo. Had a great time watching the bullets fly down range till the grass was set on fire. We continued to shoot till our 50 rounds were expended, by then the fire had burned itself out.