BRUSSELS • He lived under the rafters in a small attic apartment in the Molenbeek district of Brussels, and became known to some followers as the "Santa Claus of jihad". He had the bushy beard and potbelly, and generously offered money and advice to young Muslims eager to fight in Syria and Somalia, or to wreak havoc in Europe.
When the Belgian police seized the computer of the man, Khalid Zerkani, in 2014, they found a trove of extremist literature. In July, Belgian judges sentenced him to 12 years in prison for participating in the activities of a terrorist organisation, and declared him the "archetype of a seditious mentor" who spread "extremist ideas among naive, fragile and agitated youth".
But only in the months since then has the full scale of Zerkani's diligent work on the streets of Molenbeek and beyond become clear, as the network he helped nurture has emerged as a central element in attacks in both Paris and Brussels - as well as one in France that the authorities said last month they had foiled.
During his trial, Zerkani, 42, denied any involvement in terrorism.
But court documents and interviews with Molenbeek residents and activists, as well as with Belgian security officials, suggest that he had direct or indirect connections with several crucial figures who are now dead or under arrest in connection with the November massacre in Paris that killed 130 people and the bombings last month in Brussels that killed 32.
Take Mohamed Abrini, a former Molenbeek resident who, the Belgian authorities said on Saturday, has confessed to being "the man in the hat", caught on surveillance video accompanying the airport suicide bombers and later walking away alive. His younger brother, Souleymane, travelled to Syria with help from Zerkani, according to security officials who spoke on the condition of anonymity because they were not authorised to do otherwise. The brother reportedly died there in 2014 while fighting with the Islamic State in Iraq and Syria (ISIS).
Reda Kriket, another veteran of the conflict in Syria who was arrested in France last month in connection with the thwarted attack, stayed in Zerkani's apartment for a time and lent him his French-registered Mercedes, prosecutors said.
Belgian investigators say that Abdelhamid Abaaoud, a Molenbeek resident who commanded the November attacks in Paris, was a disciple of Zerkani. Najim Laachraoui - who the authorities suspect was the bomb-maker for both the Paris and Brussels attacks - is also believed to have been connected to his circle.
The role in Molenbeek of Zerkani, a surly man more versed in the ways of the street than in those of the mosque, helps explain why a small and not particularly destitute district of the Belgian capital keeps cropping up in relation to terrorist investigations.
Long before jihad became fashionable on the fringes, crime was endemic in parts of Molenbeek. Belgian security officials and people who know Zerkani said he had assured Molenbeek's wayward youth that past criminal convictions were not an obstacle to the Islamic cause, but a vital foundation.
"Mr Zerkani has perverted an entire generation of youngsters, particularly in the Molenbeek neighbourhood," the Belgian federal prosecutor, Mr Bernard Michel, said in February.
NE W YORK TIMES