Having mailed a farewell letter to his family back in Minnesota, Jerry O. Wolff stepped off a shuttle bus on a sunny Sunday morning and disappeared into Utah's rugged Canyonlands National Park.
"I am gone in a remote wilderness where I can return my body and soul to nature. There is no reason for anyone to look for me. Just leave me where I am," he wrote.
No trace of Wolff has been found since he was last seen May 11. Park officials assume the 65-year-old biology professor committed suicide.
Millions of people come to national parks each year to enjoy the splendors of wildlife and natural beauty, but a tiny fraction arrive with a grim agenda.
So far this year, at least 18 people have committed suicide in America's national parks, from the swamplands of the Everglades and the beaches of Cape Cod to the rain-soaked forests of Olympic National Park and the bleak expanse of the Mojave Desert.
For some, the parks are apparently just a convenient place to end it all. Others, though, seem to seek out the beauty and solace of these spots.
"Parks hold a special place in people's hearts," said Al Nash, a spokesman at Yellowstone, where five suicides have been recorded since 1997. "There are some individuals who feel it's important to have that kind of connection in those final moments."
As for Wolff, Jim Hughes, the police chief in his hometown of Sartell, Minn., said the St. Cloud State University professor had been to Canyonlands before for research. As for why he apparently took his life, Wolff had "some personal issues," the chief said, adding that he had no details.
The day after Wolff disappeared, searchers found the body of a 27-year-old man who had driven into Colorado National Monument near Grand Junction, parked on the side of a road, walked about 200 yards away and shot himself.
At the same park last October, a 57-year-old woman drove her station wagon off a 250-foot cliff. A few weeks later, a 63-year-old man drove to an overlook at the park called Cold Shivers Point, sat on a rock outcropping overlooking a valley and shot himself.
"It's become known in this area as a place that suicides are happening, but you can be sure the staff here are doing everything we can to prevent them," said Joan Anzelmo, superintendent of Colorado National Monument.
Rangers are trained in suicide prevention, and park officials are contemplating closing certain areas at night and adding more guardrails. Employees in places like the Grand Canyon are taught to keep an eye out for notes taped to steering wheels.
Ten people have killed themselves at the Grand Canyon since 2004, the most at any park in recent years, according to the National Park Service. The 1991 movie "Thelma & Louise" -- which ends with the pair driving off a cliff in a classic Thunderbird convertible -- has been blamed by some for a string of copycat suicides at the Grand Canyon, even though the scene was actually filmed at a state park in Utah.
"Maybe it's the romanticization of a suicide attempt in a spectacular place," said Michael Ghiglieri, who has co-written books about deaths at the Grand Canyon and Yosemite.
Among the stories he has recounted: A young man once asked a couple to take his picture at the Grand Canyon, then jumped to his death in front of them. Another man, who had squandered an inheritance, climbed to the top of Yosemite Falls, wrote his will -- leaving money to have a redwood planted on his grave -- then leaped off the falls, the highest in North America.
Lanny Berman, executive director of the American Assn. of Suicidology, said that when it comes to suicides in national parks, in general, "the driving force for most is availability and accessibility and, secondarily, whether that site offers something that other sites don't."
At Colorado National Monument, Anzelmo said, suicides are, in part, a reflection of nearby Mesa County, where the suicide rate is about twice the national average.
One of the first recorded suicides in national park history was that of a 27-year-old woman in Yellowstone who apparently killed herself with an overdose of morphine in 1884, just 12 years after the national park was created, according to Yellowstone historian Lee Whittlesey. Most suicides in that park's history were by park employees, he said.
"Perhaps these persons wanted their last moments to be spent in a beautiful or famous place, or perhaps they wanted their deaths somehow inextricably linked to nature," Whittlesey wrote in his book "Death in Yellowstone."
Last year, there were at least 26 suicides or probable suicides in the national park system's 391 areas, according to Bill Halainen, who compiles ranger reports daily for the National Park Service. The agency does not have complete figures for earlier years.
Halainen said he believes that the numbers fluctuate from one year to the next and that there is "no clear indication of any sustained upward trend."
This year began with a search for a 46-year-old carpenter with cancer who drove his truck to Everglades National Park, climbed into his canoe and vanished. The most recent case involved a 47-year-old man at Timpanogos Cave National Monument in Utah who called the sheriff's department from the visitors center June 10 to tell dispatchers he was going to shoot himself and where to find his body.
When people vanish, National Park Service employees and sometimes volunteers typically mount a search. Recovering bodies and vehicles, particularly when they go over a cliff, can require helicopters, rappelling and other dangerous exploits.
"Our expectation is that people are coming to the national parks to have a good time," said Maureen Oltrogge, a spokeswoman at the Grand Canyon.
"When something tragic happens, it's really difficult on the staff."