(CNN) -- An Ohio grand jury on Friday indicted a 52-year-old man, alleging that he "pulled the trigger" to kill three men who had answered a Craigslist ad for work on a cattle farm, authorities said.
Richard Beasley faces multiple counts of aggravated murder, kidnapping and aggravated robbery as well as a host of other charges, according to the 28-page indictment released Friday by the Summit County prosecutor's office.
Ohio Attorney General Mike DeWine acknowledged there may be more victims, and thus more charges.
"We are dealing with serial killings here," DeWine told reporters, pleading for the public to provide more information. "Are there more bodies? Frankly, we don't know. If there are, we need to find them."
As outlined in the indictment, Beasley is the "principal offender" in the murders of three men between August and November 2011, Summit County Prosecutor Sherri Bevan Walsh said.
He could be eligible for the death penalty if convicted, given that the murders could meet one or more requirements for that sentence including purposely causing the death of two or more people and murdering people while a fugitive, committing a kidnapping and/or committing armed robbery.
"This case deserves the death penalty for a multitude of reasons," Walsh said. "This case, we view to be one of the worst of the worst when it comes to horrible murder cases."
Beasley will be formally arraigned on the charges next Wednesday morning, prosecutor's office spokeswoman April Wiesner told CNN affiliate WJW by e-mail. He has been in custody at the Summit County jail since November 16, 2011, on unrelated charges -- including drug trafficking and promoting prostitution -- according to jail records posted online.
The victims -- 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 responding to an online ad soliciting workers, authorities have said.
The investigation into the killings began the night of November 6, when a Noble County deputy sheriff responded to a call and came upon a "white, middle-aged man being treated for a gunshot wound to the right arm," according to Sheriff Stephen S. Hannum of Noble County.
The wounded man -- who was identified in the indictment as Scott Davis, 48, from South Carolina -- told the law enforcement officer that he had answered an ad on the Craigslist website offering work caring for cattle on a 688-acre property in eastern Ohio.
He met with two males, including Beasley, and drove with them toward Stock Township, Ohio. After being told a road was closed due to a landslide, Davis got out of the car to start walking toward the property, which he was told was nearby.
Davis told the sheriff that, while walking through a heavily wooded area, he turned around "to see a gun pointed at his head. He deflected the gun and ran" -- getting shot in the arm while fleeing, the sheriff explained late last year. The victim hid for seven hours in the forest before going to a house and requesting help, Hannum said.
"Davis lived to tell the tale, but as his story got out, more information came forward about other missing persons who had answered similar Craigslist ads," said DeWine, speaking at Friday's news conference with Walsh.
The third victim, Kern, was killed one week after Davis's escape, according to authorities.
The attorney general said that the victims were all "down on their luck" men trying to take advantage of an opportunity to "have a better life."
"Tragically, it ended in their deaths," he added.
Brogan Rafferty, 16, of Stow, Ohio, who is a high school sophomore, is facing charges of aggravated murder and attempted murder in connection with the killings, and prosecutors are seeking to try him as an adult, according to CNN affiliates WKYC and WJW.
Rafferty's father, Michael, told WJW in late November that his son had been "manipulated" and "corrupted," insisting that the teenager is a "mild-mannered gentleman."
The father also said that his son unwittingly dug the graves at Beasley's direction, WJW reported. The boy's mother said her son denied killing anyone and added that Beasley portrayed himself as "a chaplain" who gave food to the homeless.
Walsh, the Summit County prosecutor, noted Friday that the judge had imposed a "gag order" in that case, "so we cannot give any comments."
As to Beasley, he will be arraigned on 27 counts -- including, besides the aggravated murder charges, four for aggravated robbery, four for kidnapping, two for grand theft and one for identity fraud -- according to the indictment.
DeWine said the case should serve as a "warning" about the potential perils of the Internet. He noted that while there are many legitimate uses for the classified website, "many people ... use Craigslist for horrible reasons."
"I'm shocked and I'm sickened by how technology and the Internet were used in this case to draw in vulnerable people and then execute them," he said.
CNN's John Fricke and Rich Porter contributed to this report.