On the evening of Wednesday, July 11, 2007, Chris Duchamp, 23, finished his electrical-engineering classes at a college in Ottawa, Ontario, and rode the bus home to his one-bedroom apartment across the river in Gatineau. Duchamp (not his real name) lived alone. Sometime around three Thursday morning, Duchamp took off his clothes. He then strung a length of boat rope through an eye hook he'd driven into the floor, looped it around his neck in a way that allowed him to control the tension, and threaded it through a second eye hook, which he'd affixed to the archway above his head. Then he took the free end in his left hand and pulled.

The next day, Duchamp, a tall, blue-eyed man whom friends affectionately described as a "smart-ass," failed to show up at the movie theater where he worked part-time.

When police discovered his body a day later, slumped over in its cat's cradle of ropes, they found something else, too: On a kitchen table, within arm's length of Duchamp, a laptop computer was flashing pornography.

"The police told me he had committed suicide," says Jean Duchamp, Chris' father (whose name has also been changed). But his son had no history of depression or mental illness. So Jean pressed the police who'd been at the scene. "I said to the officer, 'Did he have any clothes on?' He said, 'We found him hanging—it's a suicide.' I said, 'Did he have any clothes on?' He said no. I said, 'Well, it's not a suicide.'" Later, when Chris' family scoured their deceased son's computer for clues about his lifestyle, they stumbled upon something disturbing: Not only had Chris been practicing autoerotic asphyxiation (AeA) for years, his circle of friends had been doing it too. They'd even discussed it in online chat rooms. One of those posts, Jean says—left by a friend of Chris' after his death—still haunts him two years later. It read, "He wasn't supposed to do this alone."

Stories like Duchamp's have been appearing periodically in the news for years. This past June, actor David Carradine was found dead in the closet of his Bangkok hotel room, reportedly with a set of cords lashed around his neck, hands, and genitals. And 12 years before that, INXS frontman Michael Hutchence died in a Sydney hotel; he was found naked, kneeling against a door, with a belt nearby. In both cases, suicide and murder were among the initial theories. But Carradine and Hutchence weren't seeking death or pain—in fact, it's likely they were chasing pleasure. Their method—autoerotic asphyxiation—just happened to kill them. The infrequency with which we hear about such cases seems to suggest that AeA is the province of an obscure minority. But the practice may be more widespread than most of us imagine: One online fetish site for "gaspers" (a slang term for AeA enthusiasts) claims to have received 4.7 million visitors since launching in April 1992. According to an FBI estimate, between 500 and 1,000 Americans die from AeA every year—a range that's comparable to the number of homicides in New York City in 2008—and the majority of them are men. That estimate hasn't been updated since the early eighties, and some experts believe it to be conservative, because the stigma attached to the practice makes people reluctant to acknowledge AeA as the cause of death.