The teen died from a pre-existing cardiac condition after being assaulted in a bathroom

Charges have been filed against three Delaware girls in connection with last month’s high school bathroom fight that killed Amy Joyner-Francis.

In a statement to PEOPLE, the Delaware Department of Justice released the cause of the teen’s death. “The autopsy did not detect any internal injuries or significant blunt force injuries,” the statement reads. “The Medical Examiner determined that Amy died from a cardiac incident that she was vulnerable to because of a pre-existing heart condition, but the cardiac incident would not have occurred if she had not been assaulted.”

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The statement goes on to explain that only one girl is alleged to have actually struck the teen. She has been charged with criminally negligent homicide.

Because of the severity of her offense, the 16-year-old girl will tried as an adult in the Superior Court. If convicted, she faces up to eight years in prison.

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Two other girls were charged with criminal conspiracy. “Delaware law does not allow for a charge of conspiracy to commit negligent homicide,” the Department of Justice said in the statement. “Therefore, [they] were charged with third degree criminal conspiracy, which is the highest level of criminal conspiracy allowed by law given the facts of this case.

The two girls will be charged as juveniles. If convicted, they face up to a year in prison.

It is unclear whether the girls have retained attorneys.