I think i figured out how this works (and for those of you who figured it out before me, go easy on me, i feel good about myself!). So, the fart perpetrator has some devise attached to his gluteus maximus, and the camera man, or someone else, has a remote controlling electronic noisemakers that create various fart sounds. The sound comes through the actors "a-hole area" shall we say, and causes chain reaction of public fear, disgust, laughter, smiles, running for one's life, and of course .... panic. It's brilliant!
There once was a man from Rangoon. Whose farts could be heard on the Moon. When you would least expect them, He would crank one out of his rectum, with the force of a Typhoon!