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Perhaps the most disturbing photographs from the Holocaust captures a bespectacled German officer pointing a handgun at the head of a resigned person crouching in a suit before a trench containing bodies. German troops stand around the scene.

The image shot in present-day Ukraine was long known, wrongly, as Vinnitsa's last Jewish resident, and stayed veiled in secrecy for many years.

One German historian based in the United States has meticulously gathering the evidence and, using machine learning, claims he has discovered the killer.

Study Discoveries

According to evidence now published in a prestigious research publication, the German unit performed the mass killing on 28 July 1941, most likely in the midday, in the citadel of a Ukrainian city.

The city served as for centuries a prosperous heart of Jewish culture. Found 150km southwest of Kiev and about 56 miles to the north of what is now known in English as Vinnytsia city, which had once believed falsely to be the site of the massacre.

Mobile Killing Unit

This particular SS unit, part of various task forces sent in the newly occupied Eastern Front, had been tasked with eliminating the area of “Jews and partisans” shortly prior to a tour by Hitler himself.

One of its members was Jakobus Onnen, a teacher of French, English, and gymnastics who was born in 1906 in the rural community of Tichelwarf village, not far from the border with the Netherlands.

Investigation Process

Matthäus outlined an “incremental process” of traditional digging in historical documents, fortuitous discoveries, collaboration with colleagues and the pioneering assistance of volunteers from an digital research organization.

“This identification, from what experts tell me from the technical experts, is exceptionally close in terms of the likelihood the algorithm produces,” he commented.

Initial investigation published recently allowed the researcher to disclose the specific day, precise site and military group participating in the mass shooting, prompting public attention in Germany.

Key Discovery

An individual contacted the researcher and said he believed that, based on letters from the time period in his family records, the shooter could be his wife’s uncle, the teacher.

Relatives had eliminated written messages from the war front from the suspect in the 1990s. But they still had images of him, which the researchers were able to use for an computer-assisted comparison.

“The AI experts inform me that the fact that this is a historical photo poses challenges to achieve a 98 or 99.9% [match]” as commonly achieved in current forensic analysis, Matthäus noted.

But its close match, coupled with a substantial circumstantial evidence, provided sufficient basis to release his research.

AI in Historical Research

“Digital tools in the humanities have massively increased in use, but it’s usually for the processing of mass data, less frequently for individual case studies,” he stated about the potential for the employment of artificial intelligence in his discipline.

“This is certainly not the silver bullet – this is one tool among many. Researcher input continues to be crucial.”

Jakobus Onnen

Onnen, who had joined the Nazi party ahead of 1933, was from an well-to-do background and in his younger days pursued “journeying, learning foreign tongues”, researcher explained.

“Then follows his deployment in the occupied territories and clearly this is where he appears,” he said. “Incentive is one of the most difficult questions to explain. The reason I believe why he is standing there, the way he depicts himself – I think is designed to demonstrate power.”

The soldier was remained at past a modest position and was killed in battle in 1943.

“Involvement in a murder like that was considered normal and wouldn't earn you any kind of bonus points in these killing squads,” he explained.

Lost Evidence

Matthäus expressed disappointment that the written accounts the soldier mailed back from the battlefield which might have provided a window on to his ideology were lost. But he added that the relative who had contacted him about his suspected identity had read them decades before and characterized them as “ordinary”.

Continuing Investigation

Matthäus previously served as leader of the scholarly division of the Holocaust museum in Washington in Washington DC, where he had been employed since 1994.

A recent volume by him, titled "Framed Violence", studies the photo albums created by German soldiers on the Eastern Front during the second world war.

The researcher explained it was “very likely” the image of the atrocity, of which there are several prints, was shot by a other unit member and noted that such photographs were seen as “keepsakes” from massacres of civilians.

Victim Identification

Of the estimated twenty thousand Jewish residents in this location on the occupation in 1941, merely fifteen were left in early 1944, according to historical records.

“These mass executions in this manner went on until the very last day of the German occupation in the east,” the historian said.

“I think this image ought to be just as important as the picture of the gate in Auschwitz, because it {sh