Christian Brueckner's friend lured and sexually abused a young girl in the attic of a building where the two men once lived as neighbours, it is reported.
Convicted paedophile Brueckner, 43, is the prime suspect in the disappearance of Madeleine McCann, who vanished during a family holiday in Praia da Luz, Portugal, in May 2007.
He sold booze and snacks out of a kiosk at block of flats in Braunschweig, Germany, between 2012 and 2014, and was neighbours with a boy, then aged around 15 and living with his parents.
The neighbour, now 20 and named only as Robert M, attacked an eight-year-old girl in the attic in February 2019 and is serving a two year sentence in a young offender institution after being convicted of sexual abuse, according to German media.
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The girl was on her way home from school when she was lured into a back garden and then forced into the attic of the apartment building, a regional court in Braunschweig heard.
She managed to escape, go home and report the attack. Robert M was arrested a short time later and was jailed last December.
The German newspaper Bild described it as a case of "brutal" child abuse and said comparisons have now been drawn between Robert and Brueckner and questions raised about their friendship.
Robert lived one floor above Brueckner's kiosk and was often seen hanging out with the paedophile, it was reported.
A former neighbour, who wasn't named, told the newspaper: "The boy was often with Christian downstairs and would even write to him whenever he had no money.
"They liked each other."
The pair were seen together even after Brueckner gave up his kiosk in December 2014, neighbours claimed.
The public prosecutor's office, which is investigating Brueckner, declined to comment on whether there was a connection between him and Robert, German media reported.
It is claimed Brueckner would give toys and teddy bears to children as they passed his small store on their way to a primary school about 300 yards away.
Around that same time he allegedly fantasised in an online chat about abducting, torturing and sexually abusing a child.
Lenta Johlitz, 34, who worked for Brueckner in his shop, claimed to Bild: "Once he totally lost it when we sat together with friends and had a conversation about the Maddie case.
"He wanted us to stop talking about it. He shouted, 'The child is dead now and that’s it'."
Peter Erdmann, 64, who worked as a caretaker at the Grundschule Hohsteig primary school between 1999 and 2016, told the Sunday Mirror: "The kids would come to school holding ponies and teddy bears. They said Christian gave them to them and he always had a big bag of them in the storeroom.
“I asked him if he gave gifts to the kids and he told me he had a box full of such gifts in the kiosk.
“I regret it and not being more suspicious. It is gut-wrenching and I am disgusted by what I read about him.”
Mr Erdmann said he didn't think anything of it at the time and would visit the kiosk, where Brueckner was friendly and would give him free shots of Jagermeister.
There is no suggestion Brueckner abused any of the school’s pupils or the kids in the kiosk.
Neighbours have said Brueckner lived in his flat with his 17-year-old girlfriend and pet dogs, and would throw drug and booze-fuelled parties inside the building.
They claim he beat his girlfriend and once attacked her after she found child abuse images on his computer, and say they were scared of him because he was "very aggressive" and "threatening".
A neighbour named Norman claimed Brueckner left his flat in a filthy condition with "vomit and insects everywhere" when he gave up the kiosk and moved out.
The neighbour claimed Brueckner went back to the Algarve and left two dogs to die of thirst in his flat, and also alleged that Brueckner returned and threatened him with a knife while demanding he take a freezer and air-conditioning unit he had left behind.
In 2016, while police were investigating the disappearance of five-year-old Inga Gehricke, who has been called the "German Maddie", they found an online chat where Brueckner allegedly fantasised about abducting sexually abusing a child.
He allegedly told in 2013, when he was still running the kiosk, how he wanted to “catch something little and use it for days” and, regarding the risk of being caught, added: “Meh, if the evidence is destroyed...”
He allegedly added: “Then I’ll record maaaany videos/clips. I’ll document in detail how she’s being tortured.”
Police said there was no evidence linking Brueckner to Inga's disappearance, and he was not charged.
He was jailed over child abuse images found on computer memory sticks at a ramshackle former factory he owned 40 miles from the forest where Inga was last seen alive during a family picnic in May 2015.
Police raided the disused factory, where they seized a motorhome and excavated parts of the property.
A new Spiegel TV documentary claimed girls' swimming costumes, children's clothes and 8,000 child abuse images were found by police. Brueckner does not have any children.
The swimwear and clothes were found in the red and white Tiffin Allegro Bay motorhome Brueckner bought in Germany in 2010, three years after Maddie's disappearance.
Computer memory sticks contained more than 8,000 files, mostly pictures and videos of child abuse, the documentary claimed.
It alleged some of the victims in the images were infants and about 100 of the files were photos of Brueckner partly naked or wearing black stockings and committing a sex act.
The items were in a carrier bag buried beneath the body of Brueckner's dog.
Brueckner allegedly boasted a motorhome he owned and drove repeatedly between Germany and Portugal was ideal for hiding "drugs and children".
A former ambulance driver who met Brueckner and saw the RV alleged in the Spiegel TV documentary: "He told me, 'I can transport children, kids, in this space. Drugs and children, you can transport them in this van, it's a safe space in the van, nobody can find them. Nobody can catch you'."
After German prosecutors said they suspect Brueckner abducted and murdered Madeleine, police began taking another look at Inga's unsolved disappearance to find out if he was involved.
Inga's mum, Victoria, revealed this week she is clinging to hope that her daughter and Maddie are both still alive.
Inga vanished during a family picnic in a forest in northern German in May 2015, almost eight years to the day that Maddie disappeared in Portugal.
Ms Gehricke, from Schonebeck, told the Volksstimme newspaper that she was not aware of Brueckner's alleged involvement in the McCann case until it was reported by German media.
The development has given her fresh hope that Inga could finally be found and the case solved.
Ms Gehricke said: "Finally, there is a suspect in a very similar case who also appears in Inga's files. This needs to be investigated further.
"When the Maddie case is finally cleared up, I first hope that the child is alive. Perhaps a connection to the disappearance of Inga could then also be established."
She added: "We should all never give up hope that Maddie and Inga are still alive."
Ms Gehricke and her husband, Jens-Uwe, divorced after Inga disappeared.
Living under a constant "dark shadow", she said she is disappointed with the police handling of the investigation into her daughter's disappearance, and she hopes a witness will come forward and help detectives.
Inga was collecting wood for a fire when she disappeared in a forest in Wilhelmshof on May 2, 2015, during an outing with her parents and two other families.
Brueckner owned the former factory 40 miles away and was involved in a minor car accident close to the forest the day before Inga disappeared.
Meanwhile, it is claimed British police may have failed to pass on two letters sent by German prosecutors to Madeleine's parents Kate and Gerry.
Prosecutor Hans Christian Wolters, who is leading the investigation, told the Sun the first letter, sent at the end of May, said German authorities were treating Maddie's disappearance as murder.
He said the second letter was sent last week with an update on the investigation.
Both letters from German Federal Police were sent to the McCanns indirectly via Scotland Yard.
The Met Police has declined to comment on the report.
Earlier this week, Mr and Mrs McCann said in a statement they had not received any letter from German authorities.
German prosecutors suspect Madeleine is dead and have said they are investigating a 43-year-old child sex predator for murder, but admit they do not have enough evidence to charge anyone in the case.
Madeleine, from Rothley, Leicestershire, was on holiday with her parents and 18-month-old twin siblings, Sean and Amelie, when she disappeared on the night of May 3, 2007.
Mr and Mrs McCann had left their children sleeping alone in the flat at the Ocean Club complex in Praia da Luz, Portugal, while they had dinner with friends at a nearby tapas restaurant.
Brueckner was 30 at the time and had been living off and on in the Algarve area for about a decade. Police said he was travelling around in a VW camper van and living a "transient" lifestyle.
He has told his German lawyer that he wasn't involved in the McCann disappearance. The suspect, currently in jail in Kiel in northern Germany, has refused to speak to detectives.
He has racked up 17 convictions, including for sex offences against children, drug offences, theft and forgery.
Brueckner is serving a 15-month prison sentence for drug dealing and could be freed as early as July 17 if the European Court of Justice overturns his conviction for the rape of the 72-year-old American woman.
The woman was attacked in September 2005 in her flat in Praia da Luz, and Brueckner lived about half a mile from her home at the time.
Madeleine would disappear in the same resort about 18 months later.
Brueckner, who is alone in a prison cell amid fears he could be attacked by fellow prisoners, was finally apprehended in 2019 for the rape and jailed for seven years.
He is appealing his conviction, claiming German police broke law by extraditing him from Portugal on a drugs charge but then putting him on trial for rape.