The suspects knew the teen-age daughter of the victim, Robert M. Schwartz. Schwartz, 57, was found dead at his isolated farmhouse Monday after co-workers became concerned that he did not show up for work.

The Washington Post, citing unidentified law enforcement sources, reported that Schwartz was stabbed repeatedly with the sword and an "X" was carved in the back of his neck.

Police in Maryland arrested Kyle Hulbert, 18, of Woodbridge, on Tuesday. Michael Pfohl, 21, and Katherine Inglis, 19, both of Haymarket, were arrested Wednesday during a traffic stop in Manassas. All three were charged with murder.

All were acquaintances of Clara Schwartz, 19, a James Madison University student, said Loudoun County Sheriff Stephen O. Simpson.

"We don't know how familiar they were with the father, but we know they knew him," Simpson said.

Clara Schwartz has not been implicated in the slaying, authorities said.

At a bond hearing Thursday, prosecutor Robert Anderson said Inglis and Pfohl admitted their involvement.

"There were statements made that these individuals were involved in the planning, execution and cover-up of this planned assassination," Anderson said.

Hulbert was interested in witchcraft, reading books on the subject, dressing in black and forming a "coven" with friends who also were interested in the occult, said Fran Broomall, who let Hulbert stay in his Woodbridge home this fall.

Hulbert's father told the newspaper his son had been diagnosed with schizophrenia and bipolar disorder and had been off his medication for months.

"Kyle's had a rough life," Broomall said. "He was kicked around from foster home to foster home."

Pfohl had lived with Inglis and her family in Loudoun County after his parents kicked him out, said Perry Nicholson, who owns a general store across the road from the Inglis home.

"I got the impression that he was emotionally disturbed," Nicholson said.

As for Inglis, "she was kind of a retro-hippie with the tie-dyed shirts," he said. "She was a real moody kind of kid."

Pfohl and Inglis were ordered held without bond and a preliminary hearing was set for March 7. Hulbert has agreed to waive extradition proceedings and return to Virginia.

Schwartz worked at the state's Center for Innovative Technology in Herndon and was nationally known as a leading researcher on DNA sequencing analysis and biometrics.