The Feds Say a Yosemite BASE Jumper Posted His Video Online. He Claims It’s AI.

Rangers at Yosemite National Park believe they have tracked down a California man who allegedly BASE jumped inside the park last October amid the government shutdown.

How’d they catch him? Law enforcement officials say he posted a video of the illicit jump to his Instagram page. But now, the man is offering a very technologically savvy excuse. He says the video in question was generated by artificial intelligence.

According to a criminal affidavit first obtained by SFGate, federal prosecutors allege that Jack Matthew Propeck of Mission Viejo, California, made the jump on October 8, 2025. BASE Jumping is illegal in all NPS sites.

The affidavit says that a NPS ranger named Cody Hays received an anonymous tip several days after the jump occurred. The tip included screen grabs from an Instagram video showing a person BASE Jumping off of Glacier Point, a popular destination in the park.

“The video showed an individual running off a cliff and free falling through the air above Yosemite valley,” Hays’ testimony reads. “The video pans to the individuals’ face before and as he deploys a parachute.”

The screen shots were from a video that Propeck allegedly uploaded on October 8. Hays says he looked at other videos on Propeck’s page and saw the clip in question, as well as videos from other BASE jumps. The video allegedly showing Propeck jumping in Yosemite has been taken down.

“Propeck’s Instagram profile is filled with numerous videos of him BASE jumping and skydiving in numerous locations across the world,” Hays said in his testimony. “The Glacier Point video was also posted to Facebook on a profile under the same name.”

Hays said he called Propeck on October 20 to discuss the video. In the call, the affidavit states, Propeck said that he had used artificial intelligence to superimpose his face onto the video.

“He questioned why I was wasting my time with this case,” Hays said.

Hays and the NPS aren’t buying it.

Authorities have now issued a summons for Propeck to appear in court, charging him with a Class B misdemeanor. The crime is punishable by up to $5,000 in fines and/or six months in prison.

Parachuting is illegal in all national parks, except in emergencies or if the jumper applies for a permit in advance. Although the affidavit notes that Propeck told commenters on his Instagram that he had a permit to jump, Yosemite National Park does not issue permits for BASE jumping.

Parachutists have leapt from Yosemite’s cliffs since the 1980s, typically at sunrise or sunset to evade capture, but the practice is illegal. The activity received considerable attention in October, during the early days of the 43-day government shutdown. Park visitors filmed parachutists leaping from formations inside the park.

On October 24, the NPS announced that it had convicted three BASE jumpers for parachuting inside the park over the past few years.