Kyle Hulbert once called himself a protector who had "just cause" to use his 27-inch sword to kill his dear friend's father. Yesterday in court, he declared himself a murderer.

Hulbert, 19, pleaded guilty to first-degree murder and conspiracy in the Dec. 8, 2001, slaying of Robert M. Schwartz, a well-known Loudoun County biophysicist. Despite the plea, there is no agreement concerning Hulbert's punishment, and he could face life imprisonment when he is sentenced in September.

Prosecutors said Hulbert, who has a history of mental illness, was acting at the behest of Schwartz's youngest daughter, Clara Jane Schwartz, 20, when he slashed and stabbed Robert Schwartz, 57, in his remote Leesburg farmhouse. Clara Schwartz had told Hulbert that her father hit her, pulled her hair and poisoned her food, and Hulbert told police that he killed him because he was haunted by images of his friend's suffering.

During the 15-minute hearing in Loudoun County Circuit Court, Hulbert politely answered a judge's questions but did not speak about the crime. Attorney Bill Fitzpatrick said Hulbert initially had trouble understanding the gravity of the charges but recently decided a plea "was the right thing to do."

Schwartz family members did not attend the hearing. Maria Schwartz, Robert Schwartz's sister, said later in a phone interview that relatives are thankful they won't have to hear testimony about what happened. "It's a lot easier for everybody," she said. "Everybody's doing okay, but it will be nice when this is completely done."

Matt Hulbert, Kyle Hulbert's father, said he was glad his son's case was resolved without a trial, which had been scheduled to begin next week.

"I'm relieved Kyle doesn't have to [go to trial], and I'm relieved that the Schwartz family doesn't have to go through a trial," he said.

Hulbert's plea is a key moment in the story of a group of friends whose shared interest in witchcraft and the occult was at the center of one of Loudoun's most brutal and bizarre killings. Clara Schwartz is serving a 48-year prison sentence for orchestrating her father's death, and another friend, Michael Pfohl, 22, pleaded guilty to second-degree murder and is scheduled to be sentenced in April. Pfohl's girlfriend, Katherine Inglis, 20, faces a conspiracy charge in the plot. A murder charge was dropped in exchange for her cooperation.

Prosecutors said Clara Schwartz harbored a deep hatred toward her father that eventually developed into a desire to have him killed. Her musings became a murder plot, they said, when she recruited friends who shared her obsession with fantasy worlds inhabited by assassins, creatures and vampires.

A former boyfriend testified at her trial that she created a fantasy game called "Underworld" in which her character sought an assassin to kill her father. But the boyfriend said he refused to get involved when he became convinced that she was serious.

Then, in October 2001, Clara Schwartz and Hulbert met at an area Renaissance festival, and the two, who saw themselves as outcasts, bonded.

"We got close very quickly and I consider her my closest, most dear friend and as a sister as well," Hulbert wrote in a statement he gave police shortly after his Dec. 12, 2001, arrest.

Hulbert, who had bounced between foster homes and psychiatric institutions for much of the past decade, saw a chance to belong, family and friends said. He had been diagnosed with schizophrenia and bipolar disorder and suffered from hallucinations.

In his statement, Hulbert told police that he became obsessed by visions of Clara Schwartz crying and that he was convinced that her father would kill her during a planned family trip to the Virgin Islands.

On a rainy Saturday evening, Hulbert drove to Robert Schwartz's house with Pfohl and Inglis. Hulbert said he went inside alone and confronted Schwartz about the alleged abuse. Hulbert told police that he said to Schwartz: "I know your plans. You will not get away with it."

Hulbert ended his statement to police with a message to the Schwartz family: "I am sorry. I hope you can see my logic behind these actions and somehow forgive me."