Prosecutors ask court to try 16-year-old Brogan Rafferty as an adult in the three "Craigslist murders"

(CBS) - Prosecutors in Ohio filed a motion Monday asking that the teenager accused in the killings of three men who answered a Craigslist ad for work on a farm be tried as an adult.

Pictures: Prime suspect Richard Beasley charged in "Ohio Craigslist murders"

CNN reports that Brogan Rafferty, 16, and Richard Beasley, 52, face multiple charges in the case. An Ohio grand jury indicted Beasly on Friday, stating they believe he pulled the trigger.

Rafferty had a preliminary hearing Monday at which prosecutors filed the motion that he be tried as an adult. A probable cause hearing on whether to bind him over to adult court has not be set, said April Wiesner, director of communications for the Summit County prosecutor's office, according to CNN.

The high school student is charged with three counts of aggravated murder, one count of attempted murder and robbery and kidnapping. According to CNN he has entered a not guilty plea.

Ralph Geiger, 56, of Akron, Ohio; David Pauley, 51, of Norfolk, Virginia; and Timothy Kern, 47, of Massillon, Ohio; were found dead in separate shallow graves after they responded to an online ad soliciting workers between August and November of last year, authorities have said.

"We are dealing with serial killings here," Attorney General Mike DeWine told reporters. "Are there more bodies? Frankly, we don't know. If there are, we need to find them."

DeWine said that the victims were all "down on their luck" men trying to take advantage of an opportunity to "have a better life," reports CNN.

Complete coverage of the Ohio Craigslist murder on Crimesider