YOSEMITE NATIONAL PARK  (AP) — A camera on the helmet of cliff jumper Dean Potter, who died in Yosemite National Park, shows that he may have tried to avoid his friend who slammed into a ridge and then hit the rocks himself a split second later, a park official said.

It’s not clear what went wrong, but authorities are using the video captured by Potter’s GoPro and other images to reveal how he and Graham Hunt — both wearing wingsuits — died in the illegal stunt.

Mike Gauthier, the park’s chief of staff, said images show that several seconds after the jump, Hunt clipped the right side of a notch in a ridge. Potter swooped left possibly to miss Hunt, Gauthier said, but then hit the rocks just beyond Hunt on the opposite side of the notch.

“It could have been an evasive maneuver,” Gauthier told the San Francisco Chronicle in a Tuesday report. “Someone else said they saw a clipped piece of a tree up there, so we don’t know for sure.”

The two men jumped at dusk Saturday from Taft Point, 3,500 feet above the valley floor. They wore batlike suits designed to glide them downward at 100 mph from the cliff face, through rocky outcroppings and over trees to a safe landing. Instead, they died instantly, and their bodies were found 50 yards apart.

Park officials are using video from the camera mounted on Potter’s helmet and other still photo images taken by observers to re-create the accident, the newspaper reported. Potter’s girlfriend, Jenn Rapp, shot video of the launch and heard two impact sounds, Gauthier said.

Potter, 43, and Hunt, 29, were both experienced in the extreme sport of wingsuit flying, a more dangerous offshoot of BASE jumping — parachuting off buildings, antennas, spans such as bridges and Earth. It is illegal in all U.S. national parks, and jumpers who are caught are fined and have their equipment confiscated.

At least five people have died in BASE jumping accidents in U.S. national parks since January 2014, including the most recent deaths at Yosemite, said Jeffrey Olson, a National Park Service spokesman. The deaths of Potter and Hunt remain under investigation.

“In this sport you have a fraction of a second to make a life-or-death decision,” said Tom Evans, a Yosemite photographer, who writes about rock climbing. “Just one instant of inattention is all you need.”