In the videos it sounded to me like echos of the original sound of a single weapon firing. The echos often if not always seemed to me to die off about 1/2 second after the louder weapon firing sound. At the speed of sound (~767 ft/s) that could be a reflected sound path ~383 ft longer than the primary source aimed halfway between the sound source and the sound receptor, something as easy as a nearby flat vertical building surface, or even an evening temperature inversion layer in the air.
That’s a possibility too.
The 767 number is actually speed of sound in mph. In ft/s the actual speed of sound in air is ~1125 ft/s.