New Castle County Police said in a news release the attack took place on Dec. 11 in the community of Bear, located south of Wilmington.
The girl was heading home on the school bus when a schoolmate stole her phone and then forced her into a house where she was then repeatedly raped by the four boys, according to court reports obtained by The News Journal of Wilmington.
The documents obtained by the newspaper said the girl resisted and said "no" more than 15 times.
After the attack, two of the boys pointed a kitchen knife at the girl and threatened to shoot her if she told anyone, the paper reported.
The four boys were arrested Wednesday after authorities uncovered evidence linking the suspects to the crimes, including video of the rape recorded on the victim's cellphone.
The four boys are charged with various offenses, including felony rape, kidnapping and unlawful sexual contact, according to police. A hearing is scheduled to determine if the four will be prosecuted as adults, according to local reports.
Two of the boys were also charged with aggravated menacing because they allegedly threatened the victim with a weapon and "warned her not to tell anyone," police said.
Detectives are also concerned there may be additional victims, and are asking that anyone with information contact the New Castle County Police.