Dean Potter knew the risks every time he flew off a cliff in a wingsuit.

The extreme athlete lost a friend to a BASE jumping accident last year, and spoke about the death-defying nature of the sport at that friend's memorial service.

Potter was one of two men killed after jumping from a 2,300-meter promontory called Taft Point in Yosemite National Park. Some media reported that the pair smashed into a rocky outcrop when they tried to fly through a narrow gap in the mountains.