There were reports he shouted "Allahu Akbar" before murdering the two female officers and a 22-year-old man on Tuesday morning, but those claims have not been confirmed by the Belgian authorities.
The Liege prosecutor's office said the gunman had "hunted down" the two police officers, who were checking parking meters, before attacking them from behind with a knife on Tuesday morning.
One of the police officers was named in local media reports as Lucile Garcia, who was in her 50s and described by colleagues as a "fantastic woman". According to colleagues, she married her partner a month ago. The civilian victim was named by local press as Cyril Vangriecken, a 22-year-old from Vottem, a nearby town.
After stabbing them multiple times, Herman took the officers' guns and shot them both dead. He opened fire on the man, who was in a car, before taking a cleaning woman hostage in the entrance to a nearby high school.
Two other police officers were injured in the legs in the ensuing shootout at the school gate before Herman was "neutralised" by elite officers.
The cleaner was reported to be "safe and healthy". Pupils at the school, which will be closed until Thursday, were evacuated and have been offered counselling.
Belgian media reported that Herman could have killed hours before the shooting, linking him to a murder in On, in the Belgian province of Luxembourg. The body of a man shot in the head was found after a jewellery robbery in Rochefort earlier that evening.
Images on social media showed people fleeing for safety on Liege's central boulevard, with shots and sirens being heard in the background.
One video showed two police in body armour moving into position. Shots were heard at 9.30am local time (10.30am BST). The gunman was confirmed dead around 30 minutes later.
Charles Michel, the prime minister of Belgium, condemned the "blind and cowardly violence" in Liege and offered his support for the victims and their families. Mr Michel and Philippe, the King of the Belgians, have visited the city.
A minute's silence will be held tomorrow and flags flown at half-mast at Liege's town hall, where a book of condolences has been opened.
Emmanuel Macron, the president of France, expressed the "solidarity of the French people with the Belgian people" after hosting an international peace conference on Libya.
Belgium's anti-terrorist crisis centre was monitoring the situation, Interior Minister Jan Jambon said on Twitter. The country's terror threat level remains on two, which represents an "unlikely" terror threat.
Liege, an industrial city close to the German border in the French-speaking Wallonia region, was also the scene of a shooting in 2011, when a gunman killed four people and wounded over 100 before turning the gun on himself.
Belgium has been on high alert since a Brussels-based Islamic State cell was involved in attacks on Paris in 2015 that killed 130 people and Brussels in 2016 in which 32 died.
