In the tranquil, towering landscapes of Zion National Park, a simple day of adventure turned into an unimaginable nightmare. The date was September 14, 2015, and a group of seven friends—the Valencia hiking crew—set out to explore the serene beauty of Keyhole Canyon. They were experienced hikers, well-prepared, and keenly aware of the risks. Yet, what unfolded that afternoon was a catastrophe so swift and brutal it would redefine the very meaning of “safe” and leave an indelible mark on one of America’s most beloved national parks.

The Valencia hiking crew was a close-knit group of seasoned adventurers. Led by 55-year-old Don Tyner, a semi-retired manager from Los Angeles, the group included 51-year-old Gary Falco, a sales representative; 59-year-old Muku Reynolds, a special education aide; 58-year-old Steve Arthur, a traffic supervisor, and his wife Linda Arthur, 53-year-old Robin Brum, a hairstylist; and 56-year-old Mark McKenzie, a systems operator. Six of the seven were members of the Valencia hiking crew, an active community that had traveled the world together, tackling treks in places like Machu Picchu and Kilimanjaro. The seventh, Robin Brum, was a friend invited by Linda Arthur. While all were well-versed in traditional hiking, most lacked extensive technical canyoning experience, a skill only possessed by Mark McKenzie.

Canyoning, or canyoneering, is an activity that combines hiking, rappelling, and swimming through narrow gorges and canyons. Zion National Park, with its stunning slot canyons, is a prime destination for the sport. Keyhole Canyon, a relatively short and accessible slot canyon, is often chosen for its quick completion time. It’s a route that can be finished in a single day, requiring only a cheap permit and a short training class—a progression that tens of thousands of people had completed with few incidents. Tom Jones, a former guide for the Zion Adventure Company, once noted, “Canyoning isn’t an extreme sport unless you’re not very smart about it.” He went on to explain that once you descend into a canyon, you’re committed to seeing it through to the end. This commitment is what makes flash floods the single greatest danger in the sport.

The group was meticulously cautious. On the morning of their expedition, six of the seven friends enrolled in an introductory course at the Zion Adventure Company. They were made aware of the risks of flash floods and what to do in such an event. Later, as they prepared their gear, Don Tyner even called his wife to share his excitement and express some minor concerns about the weather. They were paying attention; they were doing everything right.

Just before entering the canyon, Mark McKenzie checked a Keyhole guide and a weather report on his phone. The forecast for Zion was listed as “dry.” They drove to the trailhead, looked up at the sky, and saw only clear conditions. What they couldn’t see was a massive storm brewing 15 miles to the south, a storm that was gathering unprecedented strength.

At approximately 1:50 p.m., the group reached their parking spot. They were a five-minute walk from the canyon entrance, but with no cell service, there was no way to recheck the weather. They couldn’t have known that at 2:22 p.m., just an hour and a half later, the National Weather Service would issue a flash flood warning for the entire region—a warning that came too late.

The seven friends began their descent into Keyhole Canyon sometime between 3:30 p.m. and 4:30 p.m. The last picture ever taken of all of them together shows seven smiling faces, a snapshot of pure joy and anticipation. At the canyon entrance, their path crossed with three other canyoneers—Jim Clary and his group. Jim, a seasoned guide, had chosen Keyhole specifically because of the expected weather, hoping for a quick trip. He instantly noticed the Valencia group, recognizing their rented gear and different rappelling technique. He and his group quickly passed them, a common courtesy in the canyoning community, and continued deeper into the gorge. At that moment, the weather within the canyon was perfect—blue skies and calm.

But just 15 miles away, a different reality was unfolding. A catastrophic flash flood, caused by 1.5 inches of rain falling in under half an hour, was ravaging a small town and would claim 13 lives. The deadliest flash flood in Utah’s history was on a collision course with Zion National Park.

Jim Clary’s group was nearing the end of their descent when everything changed. A deafening clap of thunder echoed through the canyon walls. Jim’s demeanor instantly shifted from calm to intense. He screamed at his companions to hurry, knowing that a flash flood could descend upon them in minutes. After finishing the final rappel, he considered leaving his rope behind for the Valencia group, but a moment of second-guessing—fearful that his advanced technique would confuse them—led him to pull it down. It was a decision he would later grapple with.

Just as Jim pulled his rope, the heavens opened. It was like a firehose turning on—one moment it was still, the next it was a torrential downpour mixed with hail. By the time Jim and his group reached the road, the water was already waist-deep and flowing at several hundred cubic feet per second. They immediately knew the seven friends behind them had no chance. The wall of water had arrived.

The search began the next morning, but the park was still a treacherous maze of mud and rushing water. On Tuesday, September 15, an off-duty guide named Kyle Anderson, along with two friends, entered Keyhole Canyon, choosing it for its relative safety amidst the continuing bad weather. As they made their way through the canyon, they found a rope on the third rappel that wasn’t theirs. Kyle peered over the edge and saw something submerged in the muddy pool below. He thought he saw a leg, but it seemed impossible. After waiting for 15 minutes with no sign of movement, he decided to rappel down himself.

As he reached the bottom, his heart sank. Tangled with the rope was a shoe, and attached to the shoe was a lifeless body. It was one of the Valencia seven. Over the next few days, all seven bodies were recovered. Some were found near the canyon entrance, while others had been swept miles downstream. Linda Arthur’s body was found an agonizing five miles from the canyon, a testament to the flood’s ferocious power.

The tragedy of the Keyhole Canyon seven was the worst canyoning disaster in American history and the deadliest accident in Zion’s 97-year history. What makes it so heartbreaking is that this wasn’t an act of recklessness. These were cautious, loving people who did their due diligence. As Steve Arthur’s son, a Ventura County Sheriff’s Department employee, said, “My mom was particularly very cautious. She would research every damn thing she could think of. That’s what shocked us… how the hell does this get past mom, of all people?”

The disaster brought to light a little-known park regulation: in Zion, guides are not permitted in many of the canyons. The park operates on a “shall-issue” permit policy, meaning they grant permits to anyone who wants one unless a flash flood warning is already in effect. This tradition, dating back to 1919, stems from a policy against commercial guiding. While rangers may dissuade visitors, the ultimate responsibility falls to the individual. For many visitors, this autonomy is precisely what makes Zion so special—the freedom to learn skills and look out for yourself.

But for the Valencia seven, it meant there was no one in the canyon to stop them, no guide with years of experience to read the subtle signs of the storm. They had no way of knowing a wall of water was building just miles away. Their deaths were a tragic, yet sobering, reminder that even when you do everything right, nature has the final say. It was a perfect storm of circumstances, a moment in time when a clear sky and a beautiful day hid a deadly secret, claiming the lives of seven friends in an instant.