Yellowstone National Park is often described as one of the most beautiful, untouched places in America. Towering geysers, steaming hot springs, endless trails—it’s the kind of landscape where families go to find peace and connection. But in October 2015, for Marcus and Sarah Chen of Seattle, it became the backdrop for one of the most disturbing predator cases in national park history.
Marcus, a 28-year-old software engineer, and Sarah, a 26-year-old pediatric nurse, were thrilled to take their 8-month-old daughter Luna on her first family adventure. Like many proud new parents, they documented every milestone online. Marcus’s Instagram posts showed their excitement, complete with photos, hashtags, and—fatally—the exact route they planned to hike. To friends, it looked like nothing more than an eager father sharing memories. To someone else, it was an opportunity.
The family’s car was later found parked at Ferry Falls trailhead. At first, rangers thought it was just another routine missing hiker case. But Detective Ray Morrison quickly noticed things that didn’t make sense. Sarah’s purse, with hundreds of dollars in cash, was untouched. Luna’s diaper bag sat perfectly arranged in the backseat, complete with her favorite stuffed elephant. No parent, Morrison knew, would ever leave without it.
Even more chilling was the GPS data. Though the car appeared at Ferry Falls, its last destination was a remote service road miles away. Someone had moved it to mislead investigators. Worse still, drag marks and blood evidence later discovered near that road suggested the family had been ambushed.
Searchers found a baby bottle near the tourist trail, giving hope the family had simply gotten lost. But forensic testing showed the formula inside was already days old, planted deliberately to throw rescuers off. Someone had studied this family, planned their disappearance, and manipulated the search effort with terrifying precision.
For three long years, the case went cold. Sarah’s sister Emma held vigils. Marcus’s parents moved away, unable to bear the pain. The FBI followed hundreds of tips, but every lead dead-ended.
Then in July 2018, everything changed. Rebecca Martinez, a geology student at Montana State, stumbled upon a moss-covered pit during her research. At first glance, it seemed like a collapsed cave. But when she shined her flashlight down, she saw something unnatural: a baby carrier at the bottom.
Investigators rappelled inside and made a horrifying discovery. The pit wasn’t natural—it had been deliberately widened with explosives, a makeshift disposal site designed to erase evidence in Yellowstone’s acidic, sulfur-rich environment. Whoever created it knew geology well enough to believe bodies would dissolve.
Inside waterproof containers, investigators found the Chen family’s belongings, eerily preserved. Marcus’s wallet carried a desperate note: We trusted the wrong person. He said there was a ranger emergency with injured hikers. We believed him. Sarah’s phone contained deleted texts from someone impersonating “Ranger Johnson,” asking for medical help. And in the most heartbreaking evidence of all, a digital recorder from Luna’s diaper bag captured the sound of zip ties, male voices, and Sarah’s final plea: “Please, she’s just a baby. Don’t hurt her. We’ll do whatever you want.”
The case no longer looked like a tragedy of one family. It looked like part of a larger pattern. Investigators soon linked the Chens’ disappearance to at least three other families who had vanished in national parks between 2010 and 2013. Each had overshared travel plans online. Each had been contacted by a supposed ranger offering secluded trails or urgent assistance. And each had disappeared without a trace.
The FBI’s behavioral analysts concluded they were dealing with a serial predator: a man who studied families, monitored their digital footprints, and used his insider knowledge of the parks to make them vanish.
Their suspect soon emerged—David Bear Kowalsski, a 47-year-old former park maintenance worker. Fired in 2015 for misconduct, he had worked in Yellowstone, Grand Teton, Glacier, and Rocky Mountain—exactly where families had vanished. His personnel file contained warnings about disturbing comments toward families, his obsessive interest in geology, and his expertise with explosives. Following a bitter divorce in 2014 that cost him custody of his own children, he spiraled into anger and obsession.
When FBI agents raided his Montana property, what they found was chilling: boxes filled with trophies from missing families, surveillance photos, maps marked with secluded trails, and chemical equipment for dissolving remains. Among the items was Luna Chen’s missing stuffed elephant.
But Kowalsski had fled. For weeks, he evaded authorities in a cross-country manhunt, leaving investigators always a step behind. Eventually, his truck was found near Glacier National Park, along with a handwritten confession. In it, he admitted to impersonating rangers, luring families, and using Yellowstone’s natural chemistry as his “perfect disposal system.”
Two weeks later, his body was discovered in a thermal pool. Whether suicide or accident, his death ensured that the families he destroyed would never get full justice. The Chens’ remains were never recovered.
The case led to sweeping changes across the National Park Service—stricter employee screening, better verification for ranger communications, and campaigns urging visitors to think twice about what they share online.
Rebecca Martinez, the student whose discovery broke the case, now works with the park service on what she calls “forensic geology”—using earth sciences to uncover hidden crimes. “Kowalsski thought he could use geology to erase evidence,” she reflected. “But the earth remembers, even when people forget.”
For the Chen family, their dream vacation turned into a nightmare that revealed a predator’s decade-long reign of terror. Their story is a reminder that even in the most breathtaking places, danger can hide in plain sight—and that trust, once misplaced, can cost everything.
