Before killing her 7-year-old son to get back at her husband, Elzbieta M. Plackowska told the boy he was going to heaven and ordered him to get on his knees and pray, prosecutors say.

Then she stabbed Justin about 100 times as he pleaded for his life and said he loved her, prosecutors said as Plackowska was denied bail this morning.

Next, she turned to 5-year-old Olivia Dworakowski who she was babysitting at the Naperville townhome and who was now begging Plackowska not to hurt her. Plackowska stabbed her about 50 times because she was a witness, prosecutors said.

Both children's throats also were slashed, prosecutors said.

Justin and Olivia had been jumping on a bed when Plackowska entered and told them to kneel, prosecutors said. "She told Justin and Olivia to get on their knees and pray. She told Justin he was going to heaven tonight," DuPage County State's Attorney Robert Berlin said in court.

Plackowska fled to a church after the slayings, then to a relative who called police. She was covered with blood when officers took her into custody, officials said.

Plackowska first told police a stalker had broken into the townhouse and killed the children, but then said she had heard voices from the devil and killed the children to save their souls, prosecutors said.

"She stated the children had evil inside of them and she was trying to drive the devil out of them," Berlin said.

Later, Plackowska told police the children didn't mind her like they should. Finally, she told police she was angry with her husband and that she would kill Justin because "she would make him hurt the way she hurt in the relationship," Berlin said.

Plackowska, dressed in a yellow jail suit, spoke little during the hearing.

When Judge John Kinsella asked if Elzbieta Plackowska was her name, she answered, "Yes."

When he asked if she could afford an attorney, she said, "No." Kinsella appointed an assistant public defender to represent her.

After the hearing, Michael Mara, a senior assistant public defender for DuPage County, spoke briefly to her.

"She seemed upset but I don't know beyond that. She is on suicide watch at the jail," Mara said. "I briefly spoke to her. It's very early in the case. Obviously, once I get the evidence I will review it with her."

The children were discovered by police shortly after 10 p.m. Tuesday after the girl's mother Marta Dworakowski, a nurse, couldn't get into the townhome after working the evening shift at a dialysis lab, according to neighbors and officials.

Police broke in and found Justin on the floor and Olivia on the bed, officials said. Two dogs were found dead in the master bedroom near the children.

Plackowska -- also identified in public records as Plackowski -- told police she had taken the children with her to a church in Naperville earlier Tuesday, then returned to the Dworakowski home in the 800 block of Quin Court, according to a law enforcement source.

At some point Tuesday night, Plackowska argued on the phone with her husband because she wanted to return to her native Poland while he wanted to remain here, the source said. Plackowska came to the United States 12 years ago on a vacation visa, officials said.

Prosecutors say her husband is a trucker who was gone from home much of the week. Plackowska told police she did not feel appreciated, and that she resented having to clean houses to pay the bills.

"She stated she was angry with her husband because he was gone most days as an over-the-road trucker," Berlin said.

But in a brief telephone interview with The Associated Press, Artur Plackowski said his wife had told him the day before the slayings that she loved him.

The husband told the AP he didn't want to talk further because he wanted to concentrate on giving his son a good funeral.

After the slayings, Plackowska drove back to the church but couldn't reach anyone, she allegedly told authorities. She also left several frantic voice messages on the church's answering machine before ultimately tossing her cellphone out the car window, officials said.

Plackowska, covered in blood, then drove to a home on Violet Circle in Naperville, where her adult son called 911, sources said. Police said they recovered two knives, one in the kitchen sink, the blade bent backward, and the other in her car.

"In all my years in law enforcement, this was the most horrific and gruesome crime scene I have seen," Naperville Police Chief Robert Marshall said after the hearing today.

Berlin called it a scene of "unimaginable horror."

Some of the officers investigating the slayings had met Olivia on her first day at school this fall, Marshall said.

The kindergartner had gone into he wrong classroom at Brookdale Elementary School and officials, unable to find her, called police and 20 to 30 officers responded, Marshall said.

The officers found her in an adjacent classroom, and some of them had lunch with her, Marshall said.

"Our officers told us she was such a sweet and loving little girl," Marshall said.

Contributing: Melissa Jenco, Vikki Ortiz Healy, Carlos Sadovi, Matthew Walberg, Erin Meyer, James Webb and freelancer Joseph Ruzich.