Belgian authorities are facing questions over why a prison inmate, suspected of links to radical Islamists in jail, was let out for a day, enabling him to carry out what police called a "terrorist attack" in the city of Liege.
The justice minister, who oversees the prison service, said he felt "responsible" for Tuesday's bloodshed in which two policewomen and a bystander were killed. The attacker was shot dead by police at a nearby school shortly afterward.
"The question of whether this man should have been given leave is striking because he killed three completely innocent people with a wish to kill himself," Koen Geens told RTBF radio.
"I have to examine my own conscience."
Islamic State claimed responsibility for the attack late on Wednesday but provided no evidence.
Interior Minister Jan Jambon said authorities were still examining the motives of Benjamin Herman, a 31-year-old Belgian drug dealer who had been in jail for years but was let out for two days on Monday to prepare for an eventual release in 2020.
But federal prosecutors said there was evidence that they were dealing with "terrorist murder".
Herman had shouted "Allahu Akbar", the Muslim affirmation of faith, during his attack and he had had contact with Islamist radicals in jail in 2016 and early 2017.
He also appeared to have followed online exhortations from Islamic State to stab police officers and use their service weapons to shoot others, prosecutors said.
Adding further evidence of an Islamist motive, a school cleaning woman who was briefly held by Herman told public broadcaster RTBF that he assured her he would do her no harm as she was a Muslim and told her to spare her tears for Palestinians and Syrians.
Confirming that Herman was also believed to have killed an acquaintance 50km away on Monday night, Jambon told RTL radio: "There are signs he was radicalised in prison but is it that radicalisation which drove him to commit these acts?
"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, it seems, he may have been on drugs."
He said that although Herman was flagged up in security reports on possibly violent Islamists in 2016 and early 2017, he had appeared to be something of a fringe figure.