AP Photo/DuPage County Sheriff's Department Elzbieta Plackowska in a booking photo provided by the DuPage County Sheriff's Department in Wheaton, Ill.

A Naperville, Ill., woman who allegedly stabbed her son 100 times and a girl 50 times told police there were "devils" inside the children that she needed to kill, according to a prosecutor.

At 40-year-old Elzbieta Plackowska's bond hearing Thursday morning, DuPage County State Attorney Robert Berlin explained Plackowska's alleged comments. "She stated the children had evil inside of them and she was trying to drive the devil out of them," Berlin said, according to NBCChicago.com.

Police say that on Tuesday Plackowska fatally stabbed her 7-year-old son Justin 100 times and 5-year-old Olivia Dworakowski 50 times, according to the Chicago Tribune. At the time, Plackowska was babysitting her son and the girl at Olivia’s home in Naperville, about 30 miles west of Chicago, the newspaper reported. She allegedly told the kids to kneel and pray before stabbing them, NBCChicago.com reported, and also told her son that he was going to heaven.

Prosecutors say both the kids' throats were slashed, the Tribune reported.

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After the murders, Plackowska tried to go to a Naperville church but found it closed, so she left a message on its answering machine saying she had done something bad and needed assistance, Berlin said, according to The Associated Press. Covered in blood and with scratches on her hands, she went to a friend's home where her other, adult son was staying and told them that she had been robbed, Berlin said.

Prosecutors say Plackowska initially told police a stalker broke into the townhouse and committed the crimes, the Tribune reported.

Plackowska later told police that she stabbed her son to death to hurt her husband who "didn't appreciate her," according to NBCChicago.com. She said she killed the girl and two dogs because they witnessed the crime, NBCChicago.com reported.

Berlin said investigators found two blood-stained knives; one in the kitchen sink at the townhome and another in Plackowska's car, according to the AP.

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"In all my years in law enforcement, this is the most gruesome and horrific crime scene that I have seen," Naperville police Chief Bob Marshall said at the news conference, according to the AP.

Plackowska is being held without bond on two counts of first degree murder, NBCChicago.com reported. Berlin said Plackowska has no prior history of violence, the AP reported.

The Associated Press contributed to this story.

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