Chelsea Johnson, missing Ohio teen, found stabbed to death in woods

(CBS/AP) FAIRFIELD, Ohio - Police in Fairfield, Ohio are now searching for the killer of 15-year-old Chelsea Johnson, who was found stabbed to death Monday about nine hours after she was reported missing.

Johnson was found behind an apartment building Monday evening about two miles from her home. An autopsy determined she'd been fatally stabbed. Johnson's mother, who reported her missing on Monday, told police the teen left home Sunday afternoon.

Investigators say they have questioned several people but so far, no charges have been filed and no arrests made, reports CBS affiliate WKRC. They do not believe her death is connected to the disappearance of another Fairfield woman, 22-year-old Katelyn Markham, who lived near Johnson and went missing on August 14, 2011.

According to WKRC, detectives say there is video of Johnson, captured by security cameras at a nearby convenience store.

Muo Salh, a manager at the convenience store, said Johnson had been in the store around 12:30 p.m. Sunday with "her neighbor," whom he had seen before but could not identify, reports the Springfield News-Sun. Salh reportedly says the neighbor bought a prepaid phone card, and then he and Johnson left.

WKRC reports that a candlelight vigil will be held for Johnson on Friday.