The students were also said to have continued to demand for ransom from her parents after killing her.
They were said to have buried their victim in a shallow grave in a forest at Ugbor village, Oredo Local Government Area of Edo State, after killing her.
It was gathered that the victim, who was kidnapped on July 29, this year, was killed four days later after she was serially molested by the suspects.
State Police Public Relations Officer, Mr Anthony Airhuoyo, however, told newsmen that the police made a breakthrough in the case on October 17 when two of the suspects were arrested.
He added that a third suspect, whose name was given as Charles, was still on the run.Mr Airhuoyo disclosed that the suspects took the police to the spot where they buried Mercy and her corpse was exhumed. He said they were awaiting autopsy report.