Tuesday's shoot-out in the Forest area of Brussels took everyone - even those French and Belgian police leading the operation, by surprise.
Local government leaders in the area described it as an "ordinary raid that went wrong".
Officers thought they were carrying out a routine search on an empty house, but when they entered the apartment they were met with a hail of bullets fired by “one or several people”.
A series of gun fights ensued and by the time calm returned several hours later, four police officers had been injured, including a French police woman, and one Kalashnikov-wielding gunman was dead.
There were initial reports of other gunmen fleeing the scene via rooftops. On Wednesday Belgian prosecutors confirmed that two fugitives were still on the run and were being actively hunted.
News of the shoot-out quickly gained worldwide media attention as speculation grew that the raid was targeting Europe's most-wanted man Salah Abdeslam, 26, the chief suspect in the Paris attacks, who fled to Brussels hours after the carnage on November 13th and remains on the run.
But officials quickly confirmed that the raid was not directly linked to the hunt for Abdeslam and later in the evening it was confirmed that the dead gunman wasn't the wanted fugitive.
The gunman has been identified as Belcaid Mohammed, an Algerian national who was was illegally in Belgium. He was found with an Isis flag and extremist material, Belgian prosecutors said on Wednesday.
Terror experts believe he may have been involved in the organization of the Paris terror attacks.
Much of the investigation into the Paris terror attacks has focussed on Belgium and in particular Brussels.
French President Francois Hollande has said that the Paris attacks, which left 130 dead and hundreds more injured, were planned in Syria but prepared and organized in Belgium. Many of the attackers, including ringleader Abdelhamid Abaaoud, were from Brussels.
A French police source told AFP the operation was focused on the associates of one, or several, of 11 people who have been charged in Belgium in connection with the attacks.
Eight of those 11 remain in police custody, awaiting trial on various terrorism charges.
While nine terrorists are known to have taken part in the actual attacks on Paris, experts believe a network numbering as many as 25 may have been involved in the logistics and organization. The fear is that these accomplices may be be planning further attacks on Paris or elsewhere in Europe.
Official sources told BFM TV that the man who rented the flat on Rue de Dries in the Forest suburb of Brussels had also rented one of the safe houses in Belgium used by the terrorists. He is said to be a 27-year-old Belgian-Moroccan.
In this safehouse, located in Charleroi around 60km from Brussels, police found DNA traces belonging to one of the Stade de France suicide bombers Bilal Hadfi and the Paris attacks ringleader Abdelhamid Abaaoud.
By midnight on Tuesday, the perimeter around the area had been reduced to a small cordon around the apartment, suggesting police didn't think there were other gunmen at large.
Local media did report that other raids were carried out in the Forest suburb later in the evening.
Meanwhile, the hunt for Salah Abdeslam and his accomplice Mohamed Abrini continues.
He was reportedly holed up for three weeks after the Paris attacks in an apartment in the Schaerbeek district in north Brussels, where police found a fingerprint, traces of explosives and possible suicide belts.
But since then the trace has gone cold.
Belgian prosecutors are due to give a press conference at 10.30 am on Wednesday.