YOSEMITE NATIONAL PARK, Calif. — 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 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.

“It could have been an evasive maneuver,” Gauthier told the San Francisco Chronicle. “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 Yosemite Valley floor. Including Potter and Hunt, at least five people have died in BASE jumping accidents in U.S. national parks since January 2014, said Jeffrey Olson, a National Park Service spokesman.