"Robert Rembert is a serial killer," prosecutor Timothy McGinty tells NBC News. "So far, we know he's purposefully executed five people." The 45-year-old truck driver pleaded not guilty to 25 felony charges Friday in connection with the deaths of four people in the Cleveland area dating back to 1997, the Plain Dealer reports. Police arrested Rembert Sept. 21, the day after he allegedly shot his cousin Jerry Rembert and family friend Morgan Nietzel—with whom he'd been living—in the head, according to NBC. After Rembert's arrest, police began looking at evidence to see if they could link him to any unsolved murders, the Plain Dealer reports.
Prosecutors say DNA evidence tied Rembert to the 1997 murder of Rena Payne, who was found raped, beaten, and strangled, the Plain Dealer reports. According to NBC, Payne's body was found in an employee restroom at a bus station, and Rembert was a bus driver at the time. The Plain Dealer reports Rembert has also been charged with the June murder of Kimberly Hall, who was similarly found strangled, beaten, and raped. According to NBC, the last calls on Hall's cellphone were to Rembert. Rembert served six years in prison in 1997 for manslaughter in the shooting death of a man named Dadren Lewis. Police are continuing to investigate Rembert, who's due back in court Thursday, the Plain Dealer reports. According to ABC News, he could face the death penalty if convicted. (Read more serial killers stories.)