During a well-being check on Halloween eve in the 800-block of Quin Court Tuesday around 10:20 p.m., police discovered the children had been slashed and stabbed to death.
Elzbieta Plackowska, 40, was charged Wednesday evening. She is scheduled to appear in bond court early Thursday morning. Police said they would hold a press conference after court.
Police said they also found two dead dogs in the home. They had also been stabbed.
Officials say Plackowska was covered in blood when she was taken into custody. She was questioned by investigators from the Naperville Police Department and the DuPage County States Attorney's Office before charges were filed.
Neighbor Robbie Johnson says Plackowska had the children at her home Tuesday.
"There was nothing unnatural about it. I just saw her with the kids," Johnson told ABC7.
"She was not a talkative person, no she wasn't," said Michelle Jones who saw the suspect.
"There is no reason to believe any additional subjects are at large at this time," said Naperville police, in an effort to calm the fears of residents who were awakened early Halloween morning to the jarring news.
The girl attended kindergarten at Brookdale Elementary School and the boy was a student at Scott Elementary School. Officials there have called in the Indian Prairie School District 204 crisis team.
"They will remain in place for as long as necessary as students work through their feelings and grief," according to a statement from the principal on the elementary school's website.
"This is an extremely difficult time, but this is an extremely strong community and I'm confident in this community and our school district that we will pull together and move through this tragic event," said Superintendent Dan Bridges, School District 203.
Witnesses were questioned after midnight in the neighborhood where the murders occurred, police said.
"To find out this, it is quite alarming," Thomas Brinson, neighbor, said.
"It's just terrible. I'm not able to get over it. I'm not able to get through my day," said Rupa Hangal whose son attends the same school as one of the victim's.
Naperville parents struggle with tragedy
On a day that's one of celebration for most kids, worried parents arrived for student pickup at Brookdale Elementary, strategizing about what to say to their children.
"I'm going to ask him if he knows what's going on first and see what he tells me then," said Gina Blizek, parent.
That was an attitude typical of the parents of students who attended the same school as the 5-year-old victim. Many received two notifications from the school about the tragedy as the day wore on.
"I will, first of all, tell them that it was personal, that it's isolated, that it doesn't have to do with anything else, there's not a murderer on the loose and that they should feel safe," said Tricia Smith, parent.
On Brookdale's website, principal Mary Howicz said, "it is with great sadness that we inform you that the Brookdale community mourns the loss of one of our kindergarten students, who passed away last night. The district's crisis team is in place this morning to support students and staff as they cope with this news."
Mother Holly Ramsburg knows the biggest struggle will be to distinguish with her kids who to trust in the future
"It's not something that goes away. I think for kids, they're pretty resilient, they'll just kinda buzz along and ask some questions, but for parents, that's the hardest part. Because you are trying to understand it, you understand how horrible it is, how precious life is. You just try to go on," Ramsburg.
Other Naperville murders
This case may bring to mind the murders of Nicholas, Emily and Thomas Lemak in their Naperville home. In March 1999, their mother, Marilyn, sedated the children then suffocated them. The former surgical nurse is now serving a life sentence for their murders.
In August 2007, police say Nimisha Tiwari set fire to her Naperville home, killing herself and her two young children. According to investigators, Tiwari was seen on video filling a can with fuel and buying toys for the children before killing them.