Prosecutors in Pennsylvania say they plan to seek the death penalty for a 30-year-old doctoral student accused of killing a 6-week-old boy she was babysitting for friends — while they took the boy’s twin brother to the hospital for injuries police say the suspect caused.

Nicole Elizabeth Virzi was arraigned on Friday on charges of murder and multiple counts of aggravated assault and child endangerment, the Pittsburgh Post-Gazette reported.

Leon Katz died on June 16, as CrimeOnline reported. Virzi, a friend of the boy’s family, was visiting that weekend from her home in California, where she was a doctoral candidate at San Diego State University and UC San Diego.

According to the criminal complaint filed against her, Virzi alerted the children’s parents to injuries on the twin, Ari, and the parents took the boy to the hospital, leaving her alone with Leon, the Post-Gazette said. Ari had scratches on his face, which she said he caused himself while flailing as she put him in a car seat.

At about 11:15 p.m. on the night of June 15, while the parents were at the hospital with Ari, Virzi called 911 and reported that Leon had fallen from a bouncer seat, bumped his head, and was becoming unresponsive. The child was taken to Children’s Hospital and pronounced dead the next morning.

A medical examiner said the boy had a severe skull fracture and multiple brain bleeds.

Virzi told police that the child had been behaving normally before she briefly fell asleep, then awoke and went to the kitchen for a bottle. While in the kitchen, she heard the boy screaming and returned to find Leon lying on the floor with a large bump on his head.

Police wrote in the complaint that she had no “plausible explanation” for the severity of the child’s injuries. Medical professionals told police that the injuries suffered by both children were unnatural and likely caused by abuse.

In seeking the death penalty, the Allegheny County District Attorney’s Office sited four aggravating factors: the murder was committed while perpetrating a felony, torture, the age of the victim, and the defendant’s history of felony convictions involving violence.

Virzi does not actually have any felony convictions at the moment, but if she is found guilty of the current charges, those convictions will count toward her sentencing, the Post-Gazette said.

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[Featured image: Elizabeth Virzi/Allegheny County Jail and Ari and Leon Katz/GoFundMe]