When you think of a mother, you imagine someone who loves you unconditionally a person to whom you give your absolute trust. But what happens when that trust is violated in the most heinous of ways? What if the woman who tucks you in at night is a mother, a murderer, and a monster?

Theresa Knorr was immoral and evil. Theresa Knorr was born Theresa Jimmie Cross in Sacramento, California. She was the youngest child in the family and very devoted to her mother. When her mother died in 1961, Cross went into a depression.

On July 9, 1966, Theresa married U.S. marine Bob Knorr. The couple had four children together: Susan in 1966, William in 1967, Robert in 1968, and Theresa "Terry" Marie in 1970. As with her first marriage, Theresa’s relationship with Bob was fraught with alcohol-fueled arguments and accusations of infidelity. The couple soon called it quits.

Knorr was physically, verbally, and psychologically abusive towards her children. After her fourth divorce, her alcoholism and abusive behavior escalated, and she also gained a tremendous amount of weight and became quick-tempered and reclusive. She disconnected the home phone and would not allow the children to have visitors.

None of Knorr's children were spared her physical, verbal, and psychological abuse. However, Knorr had a special hatred for her daughters Susan and Sheila, fueled by jealousy that the girls were growing up and blossoming into young women while she faced the prospect of growing old and losing her looks. Theresa abused and tortured her children in various ways, including burning them with cigarettes and beating them. Knorr focused her anger primarily on her daughters and trained her sons to beat discipline, and restrain their sisters.

in 1983, Knorr grabbed a 22-caliber pistol and shot Suesan in the chest. The bullet became lodged in her back, but Knorr refused to seek medical help and left Suesan to die in the family bathtub. Susan survived, so Knorr handcuffed her to a soap dish and began to nurse her back to health. Susan eventually recovered from her wounds without professional treatment.

In 1984, Suesan decided to tell her mother she would like to move out. Knorr agreed under the condition that Suesan let her remove the bullet from her back. The removal took place on the kitchen floor, using Mellaril capsules and liquor as the anesthetic. Knorr ordered Robert to remove the bullet with a box cutter. Infection soon set in and Suesan's skin turned yellow from jaundice and she became delirious. She lay dying on the floor and Knorr permitted the other children to walk over her. As Terry told Cold Case Files, Knorr told her other children that Suesan's illness was a result of possession by Satan and that the only way to purge the demon was with fire. She coerced Robert and Bill into helping her dispose of Susan. They drove her to the Sierra Nevada, Interstate 80 outside Truckee, laid her down, poured gasoline on her and burned her alive.

In 1985, Sheila also died at the hands of her mother. According to Terry, Knorr forced Sheila into becoming a prostitute and later accused her of transmitting an STD to her via a toilet seat. Thereafter, Knorr's abuse of Sheila escalated. Sheila was locked in a closet and died of dehydration and starvation several days later. Her body was packed into a cardboard box and dumped along the side of a road. She remained unidentified for years afterward.

In 1993, Terry—the youngest of the Knorr children courageously stepped forward with an account of her mother’s crimes. It was not, in fact, the first time she had reached out for help; previous attempts were dismissed. This time, however, the monstrous truth was believed. An investigation led to the arrest and conviction of Theresa Knorr, who received two consecutive life sentences. At last, Theresa Knorr was brought to justice, but the scars she left would never fade.