Brussels: The Bakraoui brothers` evolution from violent criminals to Islamist suicide bombers fits a pattern of time spent in jail for gun crime, followed by dodged parole meetings and missed opportunities to spot their drift into Islamic State`s orbit.
Brahim El Bakraoui blew himself up last Tuesday morning in the departure hall of Brussels airport. Just over an hour later Khalid detonated his bomb on a Brussels metro train.
Neither man was considered a radical threat by Belgian authorities until December, although Turkey had expelled Brahim in July 2015 believing he was trying to join fighters in Syria.
There are suggestions the brothers were radicalised in jail. Whatever the facts about their radicalisation, their case highlights the failure by Belgian authorities to keep pace with the changing profile of the Islamist danger.
Pieter Van Ostaeyen, a specialist on jihadism who has maintained contacts with Belgians fighting in Syria, said Belgian authorities had failed to find militants like the Bakraouis in time because they were looking at the "wrong list" of suspects and did not see them as counter-terrorism targets.
The Bakraoui brothers, he said, were labelled simply as gangsters and put on a list of money-motivated criminals, while authorities hunting potential Islamist radicals focused on those with established religious credentials.
"It proved wrong. Now they are merging the lists," Van Ostaeyen said.
A Belgian government official confirmed that a merging of information streams across different police agencies and specialisations was a key part of recent changes in practice.
It is belated recognition of what security officials, including the head of the EU police agency, have told Reuters are multiplying links between Islamic State militants and criminal gangs, ranging from Balkan mafias supplying guns to petty drug dealers.
These criminals` networking skills and underworld contacts are well suited to the workings of Islamist cells.
Both Bakraoui brothers were well known to police and the judiciary.
Brahim, 29, was given a 10-year sentence for attempted murder in September 2010 for firing a Kalashnikov at police and wounding one officer after a failed robbery at a Brussels money exchange office in January of that year.
He was let out on parole four years later, went missing at the end of May only to be picked up on the Syrian border by Turkish police in June 2015, having already violated his release conditions by being out of contact with his parole office.
Expelled to Amsterdam - it was his choice of destination - a month later, Belgium did nothing to detain him despite a warning from Ankara. That revelation sparked uproar this week and the offer of resignation from two Belgian ministers.
His presence in Turkey, let alone on the Syrian border, was enough to have ensured he should have been jailed on his return home, Justice Minister Koen Geens acknowledged.
"That was the only moment the link could have been made ... and we missed it," he said of the failure to realise that a man with a penchant for violence had become religiously radical.
It also took until August for him to be placed on a wanted list, and then only on a national posting. Might he have been caught if Belgium had issued an international arrest warrant?
Europol director Rob Wainwright said his agency had urged national authorities to share the maximum amount of information, but their record was patchy.
"The urgency of the terrorist threat illustrated by attacks since 2014 has demanded an improvement in that situation," he told Reuters, adding that there had been a significant increase in information shared in recent months.
The Belgian government official said he believed Brussels and Paris had set Europeans an example of cooperation since the Nov. 13 attacks in the French capital. "But up to now," he conceded, "everyone tends to keep their best cards face down."
YOUNGER BROTHER RENTED PARIS ATTACKS SAFE HOUSE
Brother Khalid, 27, was given a five-year jail term in February 2011 for car-jacking as part of a group armed with Kalashnikovs. Among the gang was a man who two years earlier had been sprung from a Brussels court by an armed accomplice who forced lawyers and police to lie on the floor.
Khalid was released on probation in December 2013 and, holding down evening service sector jobs, met his parole conditions until April 2015, when police stopped him in a car travelling the wrong way down a one-way street.
Beside him was one of the members of his earlier car-jacking gang, a man who he was barred from meeting. A court in May issued him a warning, but did not send him back to jail.
At the end of October, he disappeared.
"He did not reply to court summons, did not answer the telephone and was no longer at the address he had supplied as his residence," said prosecutor Christian Henry, adding that a court last month ordered him to return to prison, although by that time he was no longer found.
Khalid became the subject on international arrest warrant on December 11 for the charge of terrorism. He was found to have rented, under a false name, a flat used as a safe house for the Paris attackers - part of an emerging Franco-Belgian network.
Critics have said the men were let out too early. Belgian courts can grant prisoners parole after they have served only a third of their sentence. That compares with half for longer sentences in Britain and two-thirds in Germany.
Justice Minister Geens told parliament that Khalid was only released 11 months before his term was due to end, while Brahim had appeared to cooperate fully until mid-2015.
Defending his ministry, he said: "The El Bakraoui brothers` past was not as negative as it`s been portrayed this week."