Naomi Elkins, 27, of Lakewood Township, was arrested on Tuesday after admitting to killing her 1-year-old and 3-year-old children.
According to a criminal complaint, Elkins told investigators that she started having "concerning thoughts" on May 24 while her husband left for a business trip to Virginia. Elkins says she dropped her kids off at day care and spent the night praying.
Authorities say she followed a similar routine on Tuesday by taking her children to day care. After picking them up, she told police "she believed that she needed to kill the children."
READ MORE: New Jersey mother charged with murder in deaths of her 2 young children
When officers arrived at the home on Shenandoah Drive around 4:50 p.m., a serrated knife with a red handle was found in the sink and two bathtubs were filled with water.
Investigators say she stabbed her 1-year-old and then drowned both children. Emergency responders tried to perform life-saving efforts on both kids but were unsuccessful.
"She said that she counted to 50 multiple times to ensure she held them underwater for enough time," the criminal complaint states.
After drowning both daughters, she claims she realized she had done something wrong and called emergency responders.
During an interview with police, she allegedly said that she knew that it was illegal to kill her children and that what she did was wrong.
Neighbors, many of whom are members of the Orthodox Jewish community, say the family moved in a few months ago.
Elkins is being held in the Ocean County Jail. She has a detention hearing scheduled for Monday in Ocean County Superior Court.