Charleroi is located 50 km from the Belgian capital.
The guard, identified as Didier Prospero, was walking his dog when he was shot dead in the early evening on Thursday, the paper said.
His security pass was stolen, which alerted the investigators since the man was a member of a nuclear power plant staff.
The prosecutors later told DH that no links to terrorism had been discovered in the murder of the security officer.
Earlier Thursday, DH reported that Brussels suicide bombers Khalid and Ibrahim El Bakraoui were planning attacks on Belgian nuclear power stations and that the arrest of Paris attacker Salah Abdeslam had accelerated the plans of the terrorists.
The brothers reportedly planted a hidden camera in front of the home of the director of the Belgian nuclear research program. The footage with “dozens of hours” of the movements of Belgium’s nuclear boss was seized during an anti-terrorist raid in the apartment of another suspect belonging to the same terror cell, Mohammed Bakkali.
Similar information, but without the names of Brussels suicide bombers was published in DH in February.
Belgium is on high alert following the deadly Brussels attacks. On Tuesday, Brussels was rocked by twin blasts at the city’s Zaventem Airport and an explosion at the Maalbeek Metro station, just meters away from key EU buildings, less than an hour later.
Shortly after the deadly Brussels attacks, personnel from Belgium’s two nuclear power stations in Doel and in Tihange were promptly evacuated. DH also reported that soldiers have been seen at both sites in recent weeks.