A California woman was arrested in Pennsylvania earlier this month for killing a 6-week-old boy while babysitting.

Leon Katz died on June 16 after he suffered multiple skull fractures at his parents’ Pittsburgh home. Nicole Virzi, 29, had been visiting the family at the time, and she was babysitting Katz when the fatal injuries were inflicted, according to the San Diego Union-Tribune.

Virzi, who was visiting Pennsylvania for the weekend, is also accused of abusing Katz’s twin brother before Katz’s death. Virzi reportedly alerted the parents to blood in the twin boy’s diaper, leading his parents to take him to the hospital.

Virzi is believed to have caused the fatal injuries to Katz while his parents were at the hospital with his twin brother. The twins’ parents told cops that Virzi was alone with their surviving son when she told them about the blood in his diaper, the San Diego Union-Tribune reported.

Virzi claimed that Katz fell after she put him in a chair and did not strap him in. She said she was in a different room when she heard screaming and found him with a large bump on his head.

According to WTAE, a CT scan confirmed Katz suffered brain bleeds in addition to fractures to the left side of his head. Scratches and bruises were allegedly found on the surviving baby’s stomach, face, and genitals.

“The injuries sustained by both (twins are) consistent with having been sustained as a result of child abuse, as these are inflicted injuries that are not natural and not accidental,” a criminal complaint stated.

Virzi is a doctorate candidate at San Diego State University and UC San Diego. She is reportedly good friends with the victims’ parents.

Virzi is charged with homicide, aggravated assault, and endangering the welfare of children. She is due in court on June 28.

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[Featured image: Allegheny County Jail/GoFundMe]