Police say Joyner-Francis was assaulted by three students in a girls' restroom at Howard High School of Technology in Wilmington last week and died from her injuries.
Three female students have been suspended for their alleged roles in the crime. Wilmington police have designated the trio as persons of interest.
Earlier this week, the police chief said there will be charges filed, but he would not be specific about when, the exact cause of death and what the charges will be.
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"One of the things we did not want to do is we did not want to rush to judgement and place charges that could possibly be overturned or we look like we didn't know what we were doing," Wilmington Police Chief Bobby Cummings said during a town hall meeting with the community on Monday night.
As Howard High let out for the day Thursday, word circulated through parents that arrests would be coming late this week.
A law enforcement veteran close to the investigation says Joyner-Francis was thrown to the floor during the altercation, and stabbed repeatedly with pencils. Then the source says one of girls slammed her head into a sink.
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Joyner-Francis was rushed to the hospital where she was pronounced dead.
A law enforcement expert tells Action News investigations like this can take a long time because, in this age of social media, detectives have to sift through a host of Facebook and Twitter accounts, and other social media networks in the hands of minors.
"As you look at some of these sites and some of the Twitter accounts and Facebook accounts, people make a lot of statements," said Roger Carr, Wilmington University. "You have to run down every single statement, and they become voluminous and it becomes where it's so much information that it takes that much more time to be able to close the loop on the case that you thought, 'Oh this is a slam dunk.' "
Sources tell Action News one of the female students will be charged with the actual killing of Joyner-Francis. The other two will be charged as accomplices.