Two women police officers were killed besides one other on Tuesday, May 29, in Liege city in eastern Belgium by a gunman.
Since being imprisoned in 2003 he had completed 11 one-day release permits and 13 two-day periods of leave without problems.
The assailant reportedly crept up on them with a knife, stabbed them first before taking their service weapons and fatally shot them and a bystander, who was sitting inside a parked vehicle. He was then shot dead by the elite police, prosecutors said.
Dulieu said the attacker then shot and killed a 22-year-old man in a vehicle who was leaving a parking space outside a nearby high school.
The prisoner, Benjamin Herman, was on a 48-hour leave and is suspected to have killed a fourth person while on leave Monday. The killer reportedly yelled "Allahu Akbar".
The Federal Prosecution has made a decision to "federalize" the case, because there is strong suspicion that the case is a terrorist act.
He was "psychologically unstable" and wanted to "carry out attacks when released", the source said. He has been sentenced on assault, drug and insubordination charges.
He had been serving time for drug offenses.
King Philippe praised her courage after visiting her in hospital, where she was treated for shock. He then took two women hostage at a local school.
Belgian prosecutors: Deadly attack may be terror-related; gunman killed.
"I told him: 'you are in a school here, you can not come in a school, it is not right what you are doing, ' " she said.
A Belgian prison inmate who killed four people while on furlough committed "terrorist murder" and likely meant to cause more harm, prosecutors said Wednesday as authorities searched for possible accomplices and the Islamic State group claimed responsibility for the bloodshed.
But Mr Jambon said the attack was an "isolated case". However, Belgium's crisis center said it saw no reason to raise the country's terror threat for now.
Belgian media reports named the man killed before Tuesday's rampage as Michael Wilmet.
Amid questions about how two officers could have been disarmed, Mr Jambon praised the work of all involved, saying "the police did an extraordinary job".
Asked about a video from close to the scene in which someone appeared to be shouting "Allahu Akbar!" in the din, Jambon said: "My reaction is that in many terror acts, it is the last thing they shout".