FRESNO, Calif. (AP) World-famous wingsuit flier Dean Potter had strapped his iPhone to the back of his head and hit record before jumping from a cliff in Yosemite National Park in what was to be an exhilarating flight through a V-shaped rocky formation - a route that left little margin for error.
Potter set the phone at this position to capture a video of his partner, Graham Hunt, behind and above him as the pair leaped off the granite diving board at Taft Point, 3,500 feet above the valley.
Twenty-two seconds later the video abruptly stops. The two were killed when they slammed into the ridgeline at 100 mph-plus attempting to soar through the notch in the rock formation called Lost Brother.
Through a records request, The Associated Press obtained investigation reports about the deadly flight on May 16. National Park Service investigators relied heavily on Potter's bashed iPhone, interviews and a series of rapid-fire photos taken by Potter's girlfriend, Jen Rapp, who stayed behind at the launch site as the spotter.
The investigation concluded the deaths were accidental, but despite the video and photos of the jump, officials consider the specific reason why they died a mystery. Investigators listed several possible contributing factors - including indecision, distraction, miscalculation and air turbulence - as the jumpers made split-second decisions.
Potter, 43, and Hunt, 29, were both experienced in the extreme sport of wingsuit flying, a dangerous offshoot of BASE jumping - an acronym for parachuting off buildings, antennas, spans such as bridges and Earth. They would glide frighteningly close to cliffs and trees, wearing the suits that have fabric stitched between the arms and body and between the legs, so jumpers spreading their limbs can stay aloft longer and control their path with subtle body movements.
In 2009, Potter made the longest known BASE jump - off the Eiger North Face in Switzerland. He remained in flight for 2 minutes and 50 seconds, earning him National Geographic's Adventurer of the Year title.
In his final flight, Potter stood with Hunt on the ledge in Yosemite. It was still light at 7:35 p.m. with hovering rainclouds, according to the investigation. Potter wore a red suit, while Hunt's was black and yellow. Hunt zipped his phone in his pocket, after trying unsuccessfully to text his girlfriend, who was waiting in the valley. Potter's iPhone video recording captured what sounded like him saying ''Ready?''
Potter told Rapp that he planned to fly through the notch. If he lacked elevation, he would instead go around the ridgeline. Rapp snapped photos of Potter making the leap, followed closely by Hunt.
Seconds into flight, Rapp lost sight of them. Instead, she told investigators that she heard a ''thwack'' followed a second later by a ''guuuuhhh.'' She shouted in their direction, hoping the noises were parachutes opening, not impacts of bodies. She didn't received the text Potter usually sent with the word ''safe'' to assure her that he had once again beaten the odds.
Dusk turned to darkness and desperation. Rapp drove to their agreed upon meeting place. Not finding the jumpers, she returned to Potter's nearby home, where she found Hunt's girlfriend.
''Are they OK? Have you talked to them?'' Hunt's girlfriend asked. Rapp said she hadn't.
The two women at 10 p.m. went to the residence of Mike Gauthier, Yosemite's chief of staff and a friend of Potter. Gauthier urged the women to report the men missing and they made an emergency phone call. A dispatcher reported a woman calling, asking if any BASE jumpers had been arrested. Upon hearing a ''no,'' the caller broke down crying.
A ground search that night turned up nothing, but a helicopter crew the next morning found their bodies.
Autopsies found that Potter had struck headfirst and that Hunt hit with the front of his body. Blood samples showed no drugs or alcohol for either man.
Investigators say Rapp's still photos show Hunt flying left, then right, then left and a final hard banking right before his impact. After Potter's iPhone was repaired, the video shows him a foot or two above the ground just before the video stopped. Park officials did not provide the video to the AP, saying it was in possession of Potter's family. Rapp declined an AP request for the photographs that she took.
An unnamed wingsuit flier investigators consulted estimated that Potter and Hunt had flown through the notch about five times, a path well known among wingsuit fliers as being dangerous.
The flier inspected both wingsuits for the park service and found no equipment flaws, the investigative reports said.
Among other things, they noted that Hunt may have been distracted by phone calls and texts he attempted immediately before jumping and that Potter may have seen his partner strike the ground and flinched, or he simply misjudged his elevation.
''No one but Potter and Hunt will every truly know what happened,'' investigators concluded.