Woman Suspected of Stabbing Young Son 100 Times Grieving Father's Death

This Thursday, Nov. 1, 2012 booking photo provided by the DuPage County Sheriff's Department in Wheaton, Ill., shows Elzbieta Plackowska, 40, of Naperville, Ill., who was charged with first-degree murder in the deaths of her 7-year-old son and a 5-year-old girl (AP Photo/DuPage County Sheriff's Department)
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NAPERVILLE, Ill. (AP) - An Illinois prosecutor says the suburban Chicago woman charged with stabbing to death her son and a little girl she was babysitting told investigators she was upset by her father's recent death.

DuPage County State's Attorney Robert Berlin also says the woman had known the mother of the girl who died since the beginning of the school year - though their children went to different schools, and it remains unclear where the two women crossed paths.

Those details and others are emerging as investigators try to determine why Elzbieta Plackowska may have stabbed her 7-year-old son Justin 100 times and 5-year-old Olivia Dworakowski 50 times this week.

Berlin says investigators have found nothing to indicate that the 40-year-Plackowska had a history of mental illness.