• The 4-year-old died on May 31
  • Michelle Denise Shirley was arrested Thursday
  • She is scheduled to appear in court on June 30 
  • The court has set her bail at $500,000

An Arizona mother who was charged for the death of her 4-year-old son has admitted to fatally beating the child over potty training accidents.

Michelle Denise Shirley, 32, of Phoenix, was arrested Thursday for abusing and killing her son in May. According to court documents, Shirley confessed to the crime during a police interview.

The child was found unresponsive at home by his stepfather on May 31. He was later pronounced dead at the hospital.

The child suffered several injuries, including a torn spleen, lacerated liver and kidney, as well as broken ribs, News 13 noted, citing an autopsy report. He also had bruises across his back, chest, arms, legs and face. His injuries suggested that the child had been abused over a period of time, court documents indicated.

The child lived with his grandmother until she fell sick. Shirley took him to her custody in January.

Investigators found that the child had been having potty training accidents in the weeks leading to his death. He was also sad because he missed his grandmother.

The couple told investigators that Shirley was the only one who had disciplined the child. Shirley's husband said he had seen her beating the child with sandals in the past. He also told police that he had heard Shirley "whooping" the child over potty accidents the day before his death.

Shirley initially admitted to disciplining the child a month before the incident. However, she denied assaulting him the day before his demise.

When she failed a polygraphs test, she told investigators she had struck the child twice before his stepfather had found him unresponsive. She also confessed to causing bruises on her son.

"I did it. I did it. … I have to live with this, I killed my baby," Shirley told her husband after confessing to the crime, reported AZ Central.

Shirley is scheduled to appear in court on June 30 and the court has set her bail at $500,000.

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