The man who shot dead two police officers and a civilian in the Belgian city of Liège had killed someone the night before the attacks, the country’s interior minister says.
Jan Jambon said the gunman, named as Benjamin Herman, had murdered a man – a former prisoner – he met while in jail.
He added that the authorities were working to establish a motive.
The gunman also took a female cleaner hostage at a school before being killed by police.
Officials said the 31-year-old man had shouted “Allahu Akbar” (“God is greatest” in Arabic) several times during the attack.
He was let out from prison on temporary release on Monday where he had been serving time for theft and drug offences. Local media report that he may have been radicalised while in jail.
“There are signs he was radicalised in prison, but is it that radicalisation which drove him to commit these acts?” Mr Jambon said on RTL radio.
“It could have been because he had nothing to look forward to, because he also killed someone the night before, the guy’s psychology and the fact… he may have been on drugs.”