James von Brunn, who was accused of killing a security guard at the U.S. Holocaust Memorial Museum in June, died Wednesday morning at a hospital in North Carolina, his attorney said.

Von Brunn, 89, a self-avowed white supremacist, was a known Holocaust denier who created an anti-Semitic Web site called "The Holy Western Empire."

Kramer said officials from the U.S. Bureau of Prisons transferred von Brunn to an undisclosed hospital, apparently realizing his condition was worsening. Before being moved, von Brunn was undergoing mental competency tests at a prison facility in Butner, North Carolina.

The cause of death wasn't immediately known.