In the days of the Flying Avalons, circuses performed in tents -- not like they do today in colliseums and arenas.  The tents would be like the pictures you see in books -- with a pole holding it up from the center and other poles around the circumference of the tent.

The day the Flying Avalons were performing, there was a huge thunder storm.  In the middle of their act, lightning struck, creating an electric current down that center pole and onto anything else there -- the trapeze wires included.  The shock caused Harry, Anna's husband, to lose his grasp and fall below.  The lightning also caused the tent to catch fire.

Harry was sent to be buried with his uncle, an original Avalon.