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Police in Buffalo Grove, Illinois, believe a husband and father of two is responsible for killing four family members, and then himself, inside their home last week.
Buffalo Grove Police Chief Brian Budds gave the update after all five family members were found dead with "sharp force injuries" in what police had described as a "domestic-related incident."
In the latest update, police said evidence at the scene, information from investigators and the Lake County Corner's examination showed that 39-year-old Andrei Kisliak killed his family.
They say he killed his 4-year-old and 6-year-old daughters, Amilia and Vivian Kisliak, as well as his wife, 36-year-old Vera Kisliak, and mother, 67-year-old Lilia Kisliak.
Police said an animal was also found dead inside the home.
A co-worker of Vera Kisliak called the police on Wednesday, Budds said, which led to the discovery of all five family members.
Budds declined to comment on reports from neighbors that the police had been to the Kisliak home in the past month.
A local resident told the Chicago-Sun-Times she called the police in August over concerns about how Andrei Kisliak treated the children.
Police said the investigation into the case is still ongoing.
Fox News' Louis Casiano contributed to this report.