>>12186851 PB

1. I saw the flashing lights from beyond the rv in the intersection before and after the blast.

>>12186621 PB

Propane heavier than air.

RV filled with propane gas and possibly a drop line/ pipe down to the sewer under the RV (allowing some gas to leak into the sewers).

Gas spreads down and outward within the sewer pipes (across street for example) and we see the result with the sewer lid area flash across the street.