Koresh was born Vernon Howell
The mother of the notorious Waco sect leader David Koresh has been found stabbed to death at the house of a sister in Texas, police say.
Bonnie Clark Halderman, who was in her sixties, was found dead at the home of Beverly Clark who has been taken into custody pending a court appearance.
Police say they have no idea of a possible motive for her death.
She had recently written a book about her son, who led 80 people to violent death in the 1993 Waco siege.
Ms Clark Halderman was found on Friday afternoon at the home of Ms Clark, in a rural area near Chandler, about 175 miles (280km) north of Houston.
"It's still under investigation, and we really don't know what the motive was or what caused this to happen," said Henderson County Sheriff Ray Nutt.
Authorities found a knife they believe was used in the killing, he added.
The siege at Waco shocked America
Deputies had been called to the home and the two women were the only people in the house when they arrived.
Ms Clark Halderman wrote a 2007 book about her son and the cult he came to lead, called Memories of the Branch Davidians: The Autobiography of David Koresh's Mother.
Koresh and 80 of his followers, including more than 20 children, died when a 51-day armed siege of their compound by US federal security forces ended in an inferno.
Independent investigators concluded in 2000 that Koresh had been solely to blame for the deaths.