CHICAGO (CBS) — A Lakeview woman who is undergoing psychiatric care for post-partum illness has been charged with suffocating her 8-month-old son, authorities said Thursday.

While her husband went to play tennis on Feb. 7, Janet Thies-Keogh killed their son, Colin, in the couple’s home, Cook County prosecutors said.

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Colin’s autopsy initially indicated further studies were necessary but on Wednesday, a doctor with the Cook County Medical Examiner’s office ruled his death was a homicide by suffocation.

Thies-Keogh, 30, allegedly told her husband she was “not good” and asked him to come home when he called to check up on her the night Colin died. She repeatedly told him, “It’s too late,” Assistant State’s Attorney Jamie Santini said.

As the husband rushed home, he called 911 and told a dispatcher that he believed his wife may have done something to herself or their child, Santini said.

He then called his wife back and was on the phone with her for roughly four minutes, according to phone records. After that second call to his wife, Thies-Keogh’s husband called 911 dispatchers back. This time, he told them his wife indicated to him that she had “suffocated and killed” the baby, a police report said.

Officers found Colin on the bed in the master bedroom of the home in the 3900 block of North Ashland Avenue, Santini said.

He was not breathing and was unresponsive. Colin was pronounced dead later at Thorek Memorial Hospital.

Thies-Keogh was arrested this week at a residence in Des Plaines.

Judge Israel Desierto ordered her held in lieu of $500,000 bail.

Thies-Keogh’s attorney Thomas Brandstrader said his client suffers from a post-partum-related illness.

Just a month before Colin’s death, she stopped working at a beer distributing company, he said.

Thies-Keogh has been under psychiatric care since the incident and received in-patient treatment for more than a month, Brandstrader said.

Currently, she goes to outpatient therapy four days a week.

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