The US-based German historian Jürgen Matthäus has for years painstakingly assembled the puzzle pieces and, with the help of artificial intelligence, is confident he has identified the killer.

The title reads that Jürgen is the Nazi, which is incorrect.

Among them was Jakobus Onnen, a French, English and gym teacher born in 1906 in the German village of Tichelwarf, near the Dutch border.

Jakobus Onnen is the Nazi identified as holding the pistol.