Paris (CNN) -- Two teenage French girls are accused of plotting to kill family members and stabbing the little brother of one of the girls, authorities said Wednesday.
The 13-year-old girls attacked the 6-year-old boy after school on March 28, in one of the girls' home near the southern French city of Narbonne.
"When the child was attacked, he called his parents saying that he was stabbed in the neck. The parents reacted by immediately calling a doctor to treat their child. But they did not initially realize the seriousness of the injury," the Narbonne prosecutor, David Charmatz, told France Info radio.
The doctor didn't realize the seriousness of the wound when he stitched it closed, Charmatz added.
"It was only two days later that everyone realized how deep the wound was. The parents could not imagine that their own daughter and her friend had intended to kill the boy," Charmatz said.
The child remains hospitalized, but his life is not in danger, authorities said.
The two girls have been charged with attempted murder and are being held in separate institutions under the Judicial Protection of Youth Department. They are banned from contacting the victim and must be evaluated and treated by a psychiatrist.
The teenagers admitted their intention to kill other members of the family, the prosecutor said, and authorities found drawings and text messages the girls exchanged in recent weeks about their plans.
The girls recently attracted the attention of school authorities when they made cuts on their own arms. They had also told fellow classmates about their intention to kill the parents of one of the girls, the prosecutor said.
Charmatz said it's not clear why the girls wanted to harm the little boy and other family members.
"They are 13-year-old girls who are at the edge of childhood, in pre-adolescence, and they really could not explain their motivations. There is the jealousy of the little brother, but it is far from sufficient to explain such an act," he added.
An attempted murder conviction is punishable by life in prison in France, but that could be reduced to a maximum of 20 years for juvenile offenders.
Charmatz told CNN that given the young age of the two girls, and the fact that the victim did not die, a long-term prison sentence is not being considered.