A 12-year-old Tennessee girl is charged with suffocating her 8-year-old cousin as she slept while they were visiting family, prosecutors said last week. 

Home security video shows the girl, who will turn 13 this week, allegedly used bedding to suffocate her cousin on July 15 at a home in Humboldt, 98 miles northeast of Memphis, and then cleaned up the victim and re-positioned her body, authorities said.

The younger girl was sleeping in ther top bunk of the bunk beds they shared. The older girl is charged with first-degree murder and tampering with evidence.

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An image of Demeria Hollingsworth

Demeria Hollingsworth, 8, was suffocated to death in her sleep by her cousin, authorities said. (GoFundMe)

The victim’s mother, Rayana Smith, identified her as Demeria Hollingsworth, Fox 59 reported. 

"She liked to read books, go swimming, play outside, ride her bike every day, play with the kids in the neighborhood, play with my friends’ kids. My baby was sweet," Smith told the news outlet. 

Fox News Digital has reached out to Smith, who said the girls were staying with their grandmother for the summer. 

Before the killing, they had both argued over an iPhone, she said. 

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"When they told me about that, I should have just gone to get my kid," she said. "But they were having fun for the summer and I didn’t think she would kill my baby." 

Frederick Agee, the district attorney general for the 28th District in West Tennessee, said his office is petitioning Juvenile Judge Mark Johnson to transfer the child to Circuit Court to be tried as an adult, which would allow for a weightier sentence.

A Humboldt police vehicle

A Humboldt police vehicle (Humboldt Police Department)

"I consider this to be one of the most disturbing violent acts committed by either an adult or juvenile that my office has prosecuted," he said in a statement.

A service for Hollingsworth will be held on July 26, according to a GoFundMe page created by her mother. 

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Metro Nashville Public Schools confirmed to Fox News Digital that Hollingsworth attended Cockrill Elementary School. 

"The Cockrill community is mourning the unexpected loss of Demeria Hollingsworth, a beloved student who had been part of Cockrill since Pre-K. Demeria was known for her hard work, intelligence, and sweet demeanor," school Principal Casey Campbell said in a statement provided by the school district. "She was cherished by everyone who knew her. Her passing has left all of us at Cockrill devastated. She will be greatly missed."