Alaa Albakr, the brother of the suspected terrorist Jaber Albakr, had a few things to tell the German media about his sibling's suicide in police custody in Leipzig . "I, Alaa Albakr, attest that Jaber was not a terrorist, and not a member of 'IS,' and the German police killed him," he told DW on Saturday, referring to the "Islamic State."

In an interview from his home in Saasaa, not far from Damascus, where he lived with his parents and several more siblings, Alaa threatened to sue the German police and take revenge on the three Syrians who turned his brother over to authorities.

But there were several pieces of information among his occasionally emotional interviews (with DW and other German media) that may hold interest for the German security services.

Alaa said he had been in regular contact with his brother until September 2015, when Jaber told his family back in Syria that he had pledged allegiance to ISand Alaa cut off contact with him when his attempts to dissuade him failed.

"In Germany, they tried to brainwash him for while," Alaa said. "Some imams in a Berlin mosque, but it's important to know that was only for a short time, and they didn't manage it. If they had, he would have gone to Syria and not come back."

Brainwashed in Berlin?

According to Alaa, Jaber stole about 5 million Syrian pounds from his father shortly before fleeing the country in November 2014. He made it to the Bavarian border in February 2015, where he was registered as a refugee and sent to live in Chemnitz, eastern Germany.

Jaber appears to have moved around much in the first 18 months of his three-year residency permit in Germany. According to Alaa, sometime in 2015 an imam in Berlin persuaded Jaber to travel to al-Raqqa, northern Syria, to fight for IS. Jaber then returned to Germany in December.

The detail about the imams was apparently new to Germany's security forces, and a spokesperson for the Berlin branch of the BfV domestic intelligence agency told DW that it is being taken seriously. The BfV confirmed that Albakr had visited the capital at least once at the end of September this year (possibly to stake out an airport for a potential bombing attack), but underlined that up until now, Alaa Albakr is the only person to have mentioned the imams.

No suspects

There are no concrete suspects for the imams, and there is no indication that there is an unknown imam in Berlin radicalizing large numbers of young men who were about to carry out attacks. There are well-known mosques there - Al-Nur and As-Sahaba are named in the BfV's yearly reports - that preach a particularly conservative branch of Islam that German intelligence agencies call "Salafism" - but it is not known whether Albakr visited them.

Not only that, Alaa's interviews do not make clear whether the imams in question lived in Berlin or traveled there to meet Jaber.

Alaa's words need to be treated with some skepticism, according to Thomas Mücke, head of the Violence Prevention Network, an organization that runs de-radicalization programs in Germany.

"His statements are in part self-contradictory, in part absurd - when you consider for example that he is accusing the German authorities of murdering his brother in custody," Mücke told DW. "There is no evidence for any of this."

Mücke said close family members can make outlandish statements in such situations. "You often see this with relatives of people who planned or carried out attacks," he said. "He is very emotional, he's threatening the people that captured his brother with revenge, he says the police murdered him - all of this makes you think that at the moment he doesn't have both feet on the ground."

"Also, it doesn't make much sense - if you want to be radicalized you don't need to travel to Berlin," Mücke said. "There are enough places you could make contact with where you are. But radicalization is a process: It doesn't happen from one day to the next. There are questions over where it started, where it became reinforced - maybe when he went to Syria - it's all still very speculative."