A 96-year-old former member of the Waffen-SS was attacked, tied up and robbed inside his home by two unknown perpetrators posing as mailmen, German public broadcaster NDR reported.
It was unclear whether the attack was politically or criminally motivated, and police only confirmed that a break-in had taken place in a town near Hanover.
The nonagenarian appeared in a documentary that aired in November in which he admitted to participating in a 1944 revenge in Ascq, France, but claimed that the partisans were to blame for their own deaths.
The prosecutor's office in Hildesheim launched an investigation into the man after the documentary aired on suspicion that he had engaged in "inciteful speech".
The office could not be reached for comment on Friday.
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The former SS officer told NDR that the two men had stolen a folder full of documents, cash and other valuables. He added that he had been discovered by a carer who arrived at the house shortly after.