In a shocking incident, a teenage girl in India beheaded her 9-year-old niece with a sword while a religious ceremony was being held at their house.

The family of the 15-year-old unidentified girl said she "was not behaving normally" for two days before she murdered her niece Monday. The incident happened in a village in the northern Indian state of Rajasthan, Mid-day reported.

Police said the appalling incident occurred when the teen and her family had gathered in a room as part of a Hindu religious ceremony. The young girl suddenly pulled out a sword that was stored in the room and began acting erratically, police officer Govind Singh told Times Of India.

"Since her parents were in danger of being hurt, they ran out quickly. The girl then waving the heavy sword entered another room and beheaded nine-year-old Varsha, who was her niece in relation," Govind said.

When the family members returned home approximately an hour later, they discovered that she had used the sword to behead and kill her niece.

Another police officer, Narpat Singh, said the girl was studying in a school in another place and had returned home for a few days.

"The family said there was a sudden change in her behavior. She was not behaving normally and it looks like she needs treatment. The family said she had not eaten anything for two days due to the puja [religious ceremony]," the authorities said.

Women in the region often observe fasts for the Dasha Mata puja, a Hindu ceremony that is performed to welcome prosperity and blessings.

"The accused girl was also fasting for 3-4 days," Officer Narpat told The Indian Express. "It is possible that she developed some psychological condition and not eating food had a role to play in it. Even now, she is not behaving normally."

The body of the nine-year-old child was sent for an autopsy, and a forensic team was collecting evidence.

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Representational image. A teenage girl killed her niece with a sword Image by Alex Yomare from Pixabay