Story highlights Prosecutor says family court returned child to mother 6 days before his death

Brittany Pilkington reportedly calls 911 saying her baby boy stopped breathing

It was the third son she had lost this way, and police become suspicious

Pilkington confesses that she killed all three, prosecutor says

(CNN) Emergency responders couldn't resuscitate Brittany Pilkington's 3-month-old baby Noah, when he stopped breathing Tuesday -- less than a week after a court returned him to his mother. Just like they couldn't save her 4-year-old son Gavin when he died in April. Or her 3-month-old son Niall, when he died last summer.

Authorities in Bellefontaine, Ohio, saw a pattern and had some questions for Pilkington. She gave them a macabre confession. She was then arrested on murder charges, a police statement said.

"She has confessed to placing a blanket over the faces of three of her children and holding them either face down or face up until they expired," prosecutor William Goslee told reporters Wednesday.

As to a possible motive, Goslee said: "No one could predict the behavior of this mother, a 23-year-old mother who is apparently killing her children in order to preserve the smaller family with her and her daughter and the father of the children."

Goslee said that just six days before his death, a family court judge had returned Noah and his sister to the family.

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