Alan Engelhardt, 57, and Marlene Gacek, 73, were found dead at the home and Laura Engelhardt, 18, died at the hospital, said police Lt. Rich Russo. A fourth person remained hospitalized and police were questioning a fifth person who had been released from the hospital.
No charges have been filed, but police said one of the people taken to the hospital was believed to be a suspect in the stabbings. Autopsies were scheduled for Saturday and authorities did not disclose how everyone was related.
"All the parties did know each other," Russo said. "We're confident we have all the parties involved. There's no signs of forced entry. No danger to the community."
A distraught woman phoned police from the home at 6:40 a.m. Friday to report that someone was stabbed, Russo said.
By Friday afternoon, police and emergency vehicles were parked along tree-lined Bluebonnet Lane. Police patrolled outside the two-story home that has tan siding and children's playground equipment on the lawn.
"I'm really sad for that family," neighbor Tom English said. "I mean, it definitely affects everybody in the neighborhood. It's really quiet around here. We like that."
The home where the stabbings occurred is in a wooded, quaint neighborhood about 30 miles northwest of Chicago.
"It's an older part of our town," Russo said. "This is not a normal area where we have problems."
