ST JOHNS COUNTY, Fla. (WFLA) -- Authorities say a 13-year-old Florida girl who was reported missing over the weekend and later found murdered was stabbed to death. The teenager charged in connection with her murder has been ordered to be held for 21 days.

The St. John County Sheriff's Office announced Tuesday that a medical examiner had determined that the cause of death for 13-year-old Tristyn Bailey was "sharp force trauma by stabbing." The manner of death has been ruled a homicide.

A 14-year-old boy was arrested and charged with second-degree murder in connection with Bailey's death, St. John County Sheriff Robert Hardwick announced Monday.

The 14-year-old had a virtual detention hearing Tuesday morning during which a judge agreed there is probable cause that an act of delinquency occurred, according to WTLV. The judge ordered that he be detained for 21 days. The state attorney's office will then decide whether he'll be tried as an adult.

Deputies say the suspect and the victim attended the same school – Patriot Oaks Academy.

Sheriff Hardwick confirmed Monday that his office was reviewing social media activity, including reports of a selfie circulating online that shows what appears to be the suspect in the back of a squad car flashing the peace sign with a caption making reference to Bailey.

"Our real-time intelligence center has captured all these videos. As much as we can, we monitor it," he said. "And fortunately with some of these things that maybe you think are detrimental to the case, actually help ... the case and don't hurt [it] because we're collecting this media, we're collecting this real-time."

Bailey was reported missing by her family Sunday morning and was the subject of a statewide missing child alert. According to deputies, a resident who went out to help search for the girl found her body Sunday evening in the woods.

A public candlelight vigil was held to honor the 13-year-old cheerleader on Monday night in St. Johns County.