A fourth person was killed by a Belgian gunman the day before he went on to shoot dead two police officers and a civilian.
Belgian Interior Minister Jan Jambon told broadcaster RTL the attacker, identified as Benjamin Herman, “also committed a murder the night before”.
The 29-year-old was killed by police after Tuesday’s attack, which left two female police officers and one bystander dead.
Soraya Belkacemi, 53, and Lucille Garcia, 45, had their handguns stolen from them by Herman before he shot dead Cyril Vangriecken, 22, who was sitting in a nearby car.
Herman, who was on day release at the time, then took a female cleaner hostage at a nearby high school before police were able to shoot him dead.
Mr Jambon said that the person who was murdered on Monday evening was a former inmate who spent time in jail with Herman.
The victim is alleged to have been killed by being hit over the head with a blunt object.
Police have revealed 36-year-old Herman was known to authorities for years, predominantly as a petty criminal with a record that included theft, drug offences and assault.