A Maryland woman known as the “exorcism killer” and “demon assassin” pleaded guilty Monday to murdering two of her children and stabbing two others in a crazed attempt to free them of demons she believed inhabited their bodies.

Zakieya Avery and her roommate, Monifa Sanford, stabbed the four children in January 2014. Avery’s 18-month-old son, Norell, and 2-year-old daughter, Zyana, died in the attack. A 5-year-old daughter and 8-year-old son were wounded but survived.

The women claimed they saw the eyes of the children blackening and believed killing them was the only way to rid them of demons. Prosecutors said Norell was stabbed more than 20 times and Zyana was choked and stabbed in the chest and back.

Avery's lawyers are expected to make the case she was not criminally responsible for her actions. If a judge agrees she could be sent to a psychiatric hospital.

Sanford was committed to a psychiatric hospital for “an undetermined amount of time” after pleading guilty to two counts of first-degree murder in January 2015, FOX45 reported.

The Associated Press contributed to this report.