The unregistered Experimental, flown by a noncertificated pilot, collided with power lines and trees during a nighttime low pass down Runway 21 at Mathis Airport in Cumming, Ga. The flight departed Mountain Airport, Cleveland, Ga., at 2015 local time. The unlighted runway was illuminated with car headlights. The airplane passed over the runway twice and on the third low pass was observed to almost hit the airports wind sock. Banking left in a northeast direction to avoid the windsock, the airplane appeared to stall and witnesses lost sight of it.