Montgomery County corrections officials said yesterday they had no explanation for the sudden death of a convicted murderer who was taken to a hospital after an apparent seizure at the county jail in Rockville.

The inmate, Michael D. Proctor, 29, was pronounced dead at 5:22 p.m. Tuesday at Holy Cross Hospital in Silver Spring, authorities said. Proctor's body was taken yesterday to the State Medical Examiner's Office in Baltimore for an autopsy, although the cause of his death probably will not be determined until the completion of tests in several weeks, officials said.

Proctor, who claimed at his trial to suffer from multiple personalities and was awaiting sentencing March 7 on first-degree murder and attempted murder charges, had been found by a guard about 1:20 a.m. Monday after having suffered an apparent seizure at the jail, said Claire Gunster-Kirby, spokeswoman for the Department of Correction and Rehabilitation.

"We do not know at this time what brought on the seizure," she said. "It was very surprising."

Gunster-Kirby said Proctor was taken to the hospital, where he was admitted to the intensive care unit, but his condition deteriorated Tuesday and he died.

In December, a Montgomery County Circuit Court jury found Proctor guilty of the 1989 shooting death of a former girlfriend and the attempted murder of a 27-year-old man. Proctor was facing two life terms at the time of his death.

At his trial, Proctor said he was not criminally responsible for the crimes because he suffered from a multiple personality disorder. Bethesda psychiatrist Richard S. Epstein testified that Proctor had six other personalities.

Epstein said he believed two of Proctor's split personalities -- Tufu, a Pekingese dog with demonic eyes, and Clarence, a Satanic follower, committed the shootings. "Clarence and Tufu in concert fired the gun," Epstein said during the trial.

Gunster-Kirby said Proctor had exhibited suicidal behavior at the jail and was alone in his cell when found early Monday. He had been confined to a special unit where inmates with emotional or pyschological problems are regularly monitored by the staff, the spokeswoman added.

Initial tests on Proctor's body for traces of drugs or toxins were negative, said Gunster-Kirby, who added that Proctor was taking no medication at the jail.