Diezel De Rupp "enjoyed doing his little dance to the Dubstep" -- electronic music propelled by drumbeats and heavy bass. In a photo, the 5-year-old looks delighted, his hair brushed upward in a peak and his shirtfront covered by the Ultimate Fighting Championship's TapouT logo, celebrating martial arts.

The boy lived in the Denver area, but on June 10, 2012, he and his father, Jeremy Rupp, were visiting friends on a farm on the eastern Colorado plains, enjoying a Polaris 500cc all-terrain vehicle, or ATV. That's not unusual in the West, where roughly 3 million of the nation's 11 million ATVs are found. Western ATVers drive more miles than riders elsewhere, and 80 percent of that driving is recreational.

Diezel De Rupp was on the back of the ATV as a local 6-year-old boy drove it around the farmhouse yard. Left unsupervised for a few minutes, the 6-year-old drove to the edge of a nearby gravel pit, where he accidentally went over a 15-foot dropoff. The young driver jumped clear, but the ATV landed on Diezel, killing him.

This heart-rending story comes from the boy's obituary, the local newspaper, and Travis Sides, one of the prosecutors who pressed felony criminal negligence charges against all four adults who were with the boys shortly before the accident and knew they were on the ATV. "It's very sad. No one wanted this to happen," says Sides, who hopes to raise awareness about the risks that ATVs pose.

It's been a chronic problem since ATVs became popular in the 1980s. If past trends hold, more than 400 people this year -- including dozens of children -- will be killed and more than 100,000 seriously injured in ATV wrecks nationwide. That's fewer than in the peak year, 2006, probably because people have become more cautious and are also less able to afford ATVs. (Sales plunged 70 percent during the recession.) The situation is still "awful," says Sue DeLoretto Rabe, an Oregonian who helped found a national group, Concerned Families for ATV Safety. She speaks from experience: Her 10-year-old son, Kyle, died in a wreck on her farm 11 years ago. He was wearing a helmet, but his ATV tipped over as he drove downhill, and he was pinned and suffocated by its sheer weight.

Recent deaths include Kaytee Eisenbarth, a 12-year-old who, on April 7, lost control of the ATV she was driving near Fort Lupton, Colo., and rolled it; like Diezel De Rupp, she was not wearing a helmet. Miranda Anderson, a 7-year-old in Utah, was riding an ATV on May 12 when the adult driver steered too close to a tree and a branch pierced her neck.

Loose regulations, the industry's marketing and political prowess, and the growing popularity of "adventure" recreation are some of the factors behind the injuries and deaths. Western rural culture has always tolerated risky behavior -- rodeos, for instance, or shooting at anything that moves (or doesn't), or driving too fast across empty spaces, sometimes while drunk.

An ATV dealer near the farm where Diezel De Rupp died, for instance, has a fun slogan -- "The Super Toy Store" --and markets the danger with a macabre logo, a drawing of a bloody skull. "If you are looking for fast and furious or just something to infuse a little adrenaline into your weekend," says the store's website, "then you have come to the right place."