Jambon confirmed that the man was a former prisoner who did jail time with Herman.
Herman had permission to leave the jail Monday but was due to return Tuesday evening, prosecutor Eric Van Der Sypt said.
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.
- Four police officers were hospitalised with gunshot wounds, including one who was hit in the femoral artery.
Amid questions about how two officers could have been disarmed, Jambon praised the work of all involved, saying "the police did an extraordinary job".
In 2016, three coordinated suicide bombings in Brussels - later claimed by Islamic State - killed 32 people, putting the country on high terror alert.
There was support from other European countries, with French President Emmanuel Macron condemning the incident as a "terrible attack" and expressing the "solidarity of the French people".
They then take on Egypt and Costa Rica before starting their World Cup campaign against Panama on June 18.
"He then took their weapons and used them on the officers, who died", Mr. Dulieu told reporters.
A gunman has shot dead two police officers after seizing their weapons, and killed a 22-year-old bystander, in a brazen attack in the Belgian city of Liege, a prosecutor said.
A police officer speaks with parents of children at a nearby high school in the eastern Belgian city of Liege on May 29, 2018, after a man killed three people including two policemen. Shortly after taking the woman hostage he ran from the school firing at police and was gunned down. "He was shot dead", the spokesman said, adding that the hostages escaped unharmed.
The man was identified by authorities as Benjamin Herman, an inmate on a two-day leave from prison.
Liege police Chief Christian Beaupere said "the goal of the attacker was to target the police". Afterwards, he shot a 22-year-old passerby in a vehicle.
Social Media / Reuters Emergency responders are seen following a shooting in Liege, Belgium, May 29, 2018 in this picture grab obtained from social media video.
A source close to the investigation told AFP that the gunman was on a special police watchlist because of his contacts with radical Islamists.
Belgium's minister of the interior, who is at the scene, tweeted, "Our thoughts are with the victims of this serious act in Liege". The killer reportedly yelled "Allahu Akbar".
Belgian federal magistrate Wenke Roggen said Wednesday that the attack was considered "terrorist murder and attempted terrorist murder".
The prime minister says Herman did not have his name on a list maintained by an anti-terror assessment group.
Belgium is not raising the terror alert level because this is being judged an isolated case rather than the launch of a coordinated campaign.