William R. Zientek, 46, of Barrington, (inset right) was charged with murder in the shooting death of Olga Duchon, 42, of Vernon Hills, (inset left) that occurred at his apartment in the 400 block of West Russell Street in Barrington on November 17, 2024. | Background Photo: Nick Rusin; Inset Photos: Provided

A man has pleaded not guilty to attacking his ex-girlfriend, who was a mother and a doctor, with a bat and then fatally shooting her in Barrington while their young child was present.

A Cook County grand jury returned a nine-count indictment charging William R. Zientek, 46, of Barrington, with eight counts of first-degree murder and one count of possession of a firearm with a revoked Firearm Owner’s Identification card.

The charges were filed on December 16, court records show.

Zientek pleaded not guilty to the charges during an arraignment hearing on Thursday.

The charges stem from a shooting that the Barrington Police Department and Barrington Fire Department responded to around 5:40 p.m. on November 17 at The Arbors at Barrington Apartments in the 400 block of West Russell Street.

Olga Duchon, 42, of Vernon Hills, was murdered in a domestic-related incident at a home in Barrington on November 17, 2024, where her three-year-old daughter was present. | Provided Photo

Police officers arrived to find Olga Duchon, 42, of Vernon Hills, suffering from a gunshot wound.

The Barrington Fire Department provided emergency treatment to Duchon.

Paramedics transported Duchon to Advocate Good Shepherd Hospital in Barrington where she was pronounced dead, police officials said.

Lake County Coroner Jennifer Banek said an autopsy performed on Duchon showed she died from a gunshot wound to the chest.

Police officials said the incident was a domestic-related incident between family members.

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Police and firefighters respond to a shooting that left Olga Duchon, 42, of Vernon Hills, who was a doctor, fatally wounded at The Arbors at Barrington Apartments in the 400 block of West Russell Street in Barrington on November 17, 2024. | Photo: Nick Rusin

Prosecutors said that Zientek and Duchon had previously been in a dating relationship and had a 3-year-old child in common.

Zientek called Duchon on November 17 to have a face-to-face conversation, prosecutors said.

Duchon drove to Zientek’s residence in the 400 block of West Russell Street and was attacked shortly after arriving.

Prosecutors said Zientek struck Duchon in the back of the head with a baseball bat.

He then struck the woman in the right temple with the bat, causing her head to split open and fracturing her skull, prosecutors said.

Crime scene tape is seen around a residence on November 18, 2024, after Olga Duchon, 42, of Vernon Hills, was fatally wounded at The Arbors at Barrington Apartments in the 400 block of West Russell Street in Barrington the day prior. | Photo: Nick Rusin

Prosecutors said Zientek shot Duchon once with a gun that had previously been reported stolen.

The stolen gun report was made around the time that Duchon obtained an order of protection against Zientek in 2021. The order of protection resulted in Zientek’s FOID card being revoked.

The couple’s relationship had come to an end due to a disagreement about Zientek keeping firearms in the home, prosecutors said.

The 3-year-old child was present in the home at the time of the murder.

Police investigate a shooting that left Olga Duchon, 42, of Vernon Hills, fatally wounded at The Arbors at Barrington Apartments in the 400 block of West Russell Street in Barrington on November 17, 2024. | Photo: Nick Rusin

Officers took Zientek into custody at the scene after they received a 911 call from the man.

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Zientek was transported to the Cook County 3rd District Courthouse in Rolling Meadows for a detention hearing following his arrest.

Cook County Judge Ellen B. Mandeltort granted a petition filed by the state’s attorney’s office to detain Zientek in custody pending trial.

Mandeltort said no conditions of release could protect the community from Zientek and that he poses a real and present threat.

Police respond to a shooting that left Olga Duchon, 42, of Vernon Hills, (left) fatally wounded at The Arbors at Barrington Apartments in the 400 block of West Russell Street in Barrington on November 17, 2024. | Photo – Left: via Maria Hrycelak; Photo – Right: Nick Rusin

Duchon was a doctor in endocrinology affiliated with Northwestern Medicine as a member of the organization’s medical staff treating patients independently.

She was also an assistant professor at Rosalind Franklin University of Medicine and Science.

“We are learning about this tragic event in real time and we are devasted to hear this news. Our sympathies go out to her family during this difficult time,” a spokesperson for Northwestern Medicine said.

A statement from Duchon’s family said she was a “beloved physician and radiant soul” who was a “beacon of hope and healing for people around her.”

“Her exceptional skills and heartfelt compassion made her a trusted figure among her patients and a source of pride for her family,” the statement said.

The family said Duchon’s life was cut short by domestic violence, a “harrowing reminder of the dangers many face in silence.”

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“Her loss is not just a personal tragedy; it highlights the urgent need to confront and address domestic violence in our communities,” the family said.

Maria Hrycelak, the President of the Ukrainian Medical Association of North America Foundation, told news outlets that Duchon had been the featured speaker during a lecture on obesity management through the use of weight loss medication.

Police respond to a shooting that left a 42-year-old woman, who was a doctor and mother of a young child, fatally wounded at The Arbors at Barrington Apartments in the 400 block of West Russell Street in Barrington on November 17, 2024. | Photo: Nick Rusin

The lecture was held in Wheeling on the afternoon of November 17, just hours before her death.

Hrycelak described Duchon as “well-trained” and “smart.”

An obituary for Duchon said she was a “radiant and generous young woman” who had “so much to give and so much life to live.”

“Her untimely and tragic passing has left us all in shock, and she will always remain in our hearts and memories as our angel. She will be profoundly missed by all who knew her,” her obituary said.

Zientek, who remains held in the Cook County Jail, is scheduled to appear in court again on February 19 for a discovery hearing.