The man shot dead by police in Paris last week was known to German authorities. He operated under many aliases, but his real identity remains unclear.
Who was the suspected Islamist attacker shot and killed by French police last week as he ran up to a Paris police station, wearing a fake explosives vest and wielding a butcher's knife?
According to the North Rhine-Westphalian State Office of Criminal Investigation (LKA), the man lived in a refugee shelter in the western German town of Recklinghausen last year, and was apparently known under several identities across Europe.
How can the man have sought asylum in different states, used at least seven identities, and not raised alarm bells?
"It's a mystery how he could have done that," Karl Kopp of Germany's Pro Asyl group told DW. After all, states are obligated to take the refugees' fingerprints,and file them in the Eurodac database when they register the asylum seekers.
But Kopp conceded the situation was very chaotic last year. "Even though the data may in fact be there, the authorities seem not to know how to use them."
The fact is, as hundreds of thousands of refugees poured into the country last year, authorities found they were been strained to the limit - and registration took weeks.
This case shows that we need better coordination on a European level, says Jörg Radek, deputy chairman of Germany's Federal Police Union (GdP). Germany also needs to revamp its system, he told DW: "Every agency has its own database; there's no exchange - that's a fundamental problem."
Abusing the system
Germany's Federal Office for Migration and Refugees (BAMF) told DW on Monday that in general, multiple refugee registrations with German authorities also can't be ruled out - at the border, in refugee camps and when a refugee actually applies for asylum. The IT systems are not compatible, which doesn't make things easier. Sometimes, the BAMF said, refugees simply leave Germany and continue their journey northward to their actual destination, Scandinavia.
The Paris attacker'strue identity hasn't yet been established, the LKA has said, publishing a photo (above) in the hope that someone will recognize him. French investigators said on Monday a woman claiming to be the man's mother claimed he was Tunisian.
Both French and German authorities said that the dead attacker carried papers identifying him as Tarek Belgacem.
French police initially had him registered as Moroccan under the name Ali Salah, while he registered in Germany as Walid Salihi from Syria, the LKA said in a press release on Sunday.
Uwe Jacob, the state's LKA director, said it wasn't clear whether the attacker - known to police for offenses such as drug dealing, causing physical harm and harassment of women - was a Syrian, Moroccan or perhaps Tunisian. Another one of his aliases, the LKA says, was Georgian.
The man was under investigation for painting several flags commonly associated with the militant "Islamic State" ("IS)" group on the walls of two rooms at the German refugee shelter.
French authorities said the man was carrying an "IS "banner at the time of the attack. French police also found a handwritten note on his body in which he pledged allegiance to the "Islamic State" group. But according to Jacob, current information indicated that the Paris incident was a lone wolf attack.
On Saturday, German investigators raided the apartment at the Recklinghausen refugee shelter, securing "comprehensive evidence," fingerprints, DNA, documents in Arabic, SIM card casings and kitchen knives. They said the search did not turn up any evidence of other possible attacks.
According to German authorities, the attacker had lived illegally in France for five years, and had been traveling around Europe since 2011, requesting asylum in several countries. Faced with deportation, he would disappear and move on. In January 2014, the man came to Recklinghausen, where he requested asylum. He is said to have entered Germany for the first time in 2013.
The man had a criminal past, and spent a month in jail last year. In December 2015, he is said to have disappeared without a trace from the shelter in Recklinghausen.