Michelle Haskins' son, David Scott Rodenbarger, was being held without bond Saturday in White County Jail on a preliminary charge of murder.
Prosecutor Robert Guy told The Associated Press he would meet with investigators Monday to discuss formal charges. He declined to say whether Rodenbarger had a criminal record or a record of mental illness, but did say both possibilities were being investigated.
State police did not discuss what motive Rodenbarger might have had. They said the investigation is ongoing and they will release more information as it becomes available.
Guy said police searched the home where the stabbings occurred and a vehicle connected to Rodenbarger on Saturday morning. He did not disclose what they found.
The sleepy neighborhood on the shores of Lake Freeman has about 30 homes, most of which are summer homes that are unoccupied during winter, the Journal & Courier of Lafayette reported. Neighbors said the home where the Haskins lived was a rental.
"It's quiet here," Debbie Cetera, who has lived in the neighborhood for 18 years, told the newspaper. "It's so sad."
Superintendent Tom Fletcher told the Journal & Courier that Jillian was a student in the Twin Lakes school district, but he did not say which school she attended or what grade she was in. He said he planned to meet with the principal, guidance counselors and possibly the girl's teacher Sunday.
"When something like this happens to one of our kids, it is like a death in the family for the school," he told the newspaper. "We will do everything possible to comfort and help our other students, teachers and parents through this most difficult time."