Tinley Park police said Monday morning they're not ready to announce charges in a quadruple homicide investigation.
A mother and her three adult daughters were found shot to death in a suburban home on Sunday.
Tinley Park officials held a news conference Monday morning, but offered few new details. They did say they expect charges against the man in custody soon. They called the shootings "an act of senseless domestic violence."
Tinley Park officials speak on quadruple homicide investigation
The incident took place in the 7400-block of 173rd Place just before 11:30 a.m.
Police said when they arrived on the scene, the suspect, who has not been identified, was found uninjured inside the home with a gun.
It wasn't immediately clear if he was the same person who called 911.
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The Cook County Medical Examiner identified the victims as Majeda Kassem, 53, and her three daughters, 25-year-old twins, Halema and Zahia, and 24-year-old Hanan Kassem.
Authorities said the incident is domestic in nature, and does not present any harm to the general public.
Residents have been asked to stay away from the area.
Tinley Park said it hasn't had a crime like this since the murders of five women at a Lane Bryant store in 2008.
"It's a tragedy," Village Manager Pat Carr said. "Not only for the family, but all the surrounding neighbors that are there."
The news was disturbing for those who live nearby and knew the family.
"My daughter knows them," neighbor Charlotte Vaitkus said. "She went to school with the oldest son, and she employed the twin sisters. She always talked about how they were all very intelligent, and they had very high goals in life."
On Monday, the home where the incident took place remained encircled in police tape.
"I came by on my own and I seen all the different squad cars here," neighbor Archie Zientara said. "It was a quiet neighborhood; we didn't have any problems. It's just terrible, terrible, unbelievable, not in Tinley Park."
Sun-Times Media contributed to this report.
You can contact the Illinois domestic violence hotline at 1-877-863-6338 click here for more information.