Cary Stayner told a San Francisco television channel that killing women had been a powerful fantasy of his since early childhood.
He described on air how he killed Joie Ruth Armstrong, 26, last week. He also talked about murdering Carole Sund, 43, her daughter Juli, 15 - both from Northern California - and their friend Silvina Pelosso, 16, of Argentina, last winter.
"I am guilty," Stayner said. "I did murder Carole Sund, Juli Sund, Silvina Pelosso and Joie Armstrong."
Stayner, 37, confessed to police shortly after his arrest last Saturday at a nudist camp. After providing details only the murderer was likely to know, he was charged with the most recent killing, that of Joie Armstrong, whose decapitated body was discovered near the western entrance to the park last week.
Police and FBI are still checking his account of the deaths of the three sightseers, who disappeared from the park last February. Their bodies were found, burnt and mutilated, at two separate locations a month later.
The most vivid account of the killings so far came from Stayner himself, who was interviewed in his jail cell for television on Monday night. "I am guilty," he said, without showing his face on camera. "I wish I could have controlled myself and not done what I did." He said he strangled two of the tourists in their motel room, then took the third, Juli, to a lake and killed her the following morning. He insisted, however, that he had not sexually abused any of them.
The bodies of Carole Sund and Silvina Pelosso, an Argentine exchange student, were found charred beyond recognition in the boot of their rental car. Juli's head, according to the authorities, was almost severed from her body and showed evidence of having been attacked by one or more knives.
Stayner said he was the one who tipped the FBI to the whereabouts of Juli's body, sending an anonymous letter after he realised he had probably got away with his crimes. He had not planned to commit further murders, but changed his mind after a chance encounter with Ms Armstrong last week filled him with an irresistible urge to kill her.
Such urges, he said, had haunted him for almost 30 years - since he was a small boy and his younger brother, Steven, was abducted in 1972 by a drifter who kept him as a sex slave for seven years.
The unfolding saga of the Yosemite murders has horrified the local community and spooked many visitors. Some four million people, many in family groups, visit Yosemite each year to appreciate its stunning mountains and peaceful forests. Local authorities say tourism has not suffered significantly, since Stayner was apprehended almost immediately after it became clear that a serial killer was at work. But it is too soon to tell whether any prospective visitors will change their plans.
In the small mountain community where Stayner lived, residents were still reeling in disbelief yesterday at the secret life of a man who had seemed calm and friendly.
Police said they could not comment on whether Stayner's television interview was consistent with their information. However, authorities across California are now reopening old, unsolved murder cases in search of a possible link.
Kim Campbell, a model, was decapitated in Santa Barbara in 1985, while Stayner's own uncle was mysteriously murdered in his home five years later.