NAPERVILLE – The suburban Chicago woman charged with murder in the stabbing deaths of her 7-year-old son and a 5-year-old girl she was babysitting had been upset about her own father's recent death, a prosecutor said Friday.

But what role Elzbieta Plackowska's grief over her father's death may have played in her actions Tuesday – when authorities say she stabbed the two children dozens of times as they begged for their lives – DuPage County State's Attorney Robert Berlin could not say.

Berlin said previously that Plackowska told investigators she killed her son because she was upset with her husband and the girl because she was a witness. He said Friday no other explanations have emerged; as far as investigators know, Plackowska has no history of mental illness or hospitalization.