AI helps identify Nazi killer in one of the Holocaust’s most shocking photographs

The image captures all the horror of the Shoah: a Nazi points a gun at a man’s head, who looks at the camera with an almost defiant expression. Other German soldiers, and even a civilian, watch the scene without showing much emotion. It is an image of absolute evil. Before the person about to be killed lies the abyss of a mass grave filled with corpses.

This photograph, taken in Ukraine in 1941, epitomizes the so-called “Holocaust by Bullets” and is one of the best-known images of the genocide suffered by Jews under Nazism. Until now, the name of the killer was unknown. However, thanks to artificial intelligence and the collaboration of two family members, German historian Jürgen Matthäus has identified the perpetrator: Jakobus Onnen, who was 34 years old at the time and died in 1943 during an attack by Soviet partisans. The victim, however, remains unidentified. Matthäus published his finding in an article in the specialized journal Zeitschrift für Geschichtswissenschaft (Journal of History).

The research carried out by Matthäus, a historian specializing in the Holocaust who recently retired from the U.S. Holocaust Memorial Museum, where he worked as a researcher, first made it possible to correct the location of the image universally known as The Last Jew in Vinnitsa. The photograph was first published in 1961 by the now-defunct United Press (UPI) during the trial of Adolf Eichmann, one of the main organizers of the Holocaust. Eichmann had been captured by Israeli agents in Argentina, tried, and hanged — a trial on which Hannah Arendt based her famous book Eichmann in Jerusalem, in which she coined the concept of the “banality of evil.”

The image had been discovered by Holocaust survivor Al Moss, who handed it to UPI to show the world the crimes committed by the Nazis. At the time, very little information was available, and the low-resolution photograph was thought to have been taken in the Ukrainian city of Vinnytsia. It depicted the Einsatzgruppen — the death squads that carried out mass shootings of Jews in open fields in Poland and the former USSR during World War II.

It became one of the most horrifying documents of the “Holocaust by Bullets,” in which millions of people — mostly Jews, but also Roma, prisoners of war, and resistance fighters — were shot near ravines or in mass graves, almost always dug by the victims themselves, in forests or open fields near towns.

By the end of the conflict, 1.5 million Jews had been exterminated in Ukraine, according to data collected by Raul Hilberg in his monumental work The Destruction of the European Jews. Only after these mass shootings, in late 1941 and early 1942, did the Nazis begin operating extermination camps with gas chambers, where nearly three million people, mostly Jews, were murdered.

A chance discovery allowed 66-year-old Jürgen Matthäus to answer many questions surrounding the photograph — findings he published in 2023 in Holocaust and Genocide Studies. “Very little was known about that photo,” he explains in an email interview. “That changed a few years ago when the archives of the United States Holocaust Memorial Museum, where I worked as a historian until my retirement, received a donation of the war diaries of a Wehrmacht captain. One of the diary volumes dealt with the German attack on the Soviet Union in June 1941. It contained not only a good-quality copy of the photo, but also the captain’s diary entry, which confirmed the location of the crime.”

On the back of the photo was written: “Late July 1941. Execution of Jews by the SS [Schutzstaffel, Germany for Protection Squadron] at the Berdychiv Citadel. July 28, 1941.”

The Wehrmacht officer Walter Materna described in his diary that a massacre of Jews had taken place in that city, which would demonstrate that members of the regular German army were fully aware of the mass killings carried out by the SS and the death squads, even if they did not participate directly.

The next step came later, when a couple contacted the historian after reading his article, convinced that a relative of theirs was the Nazi in the photograph. It was the woman’s uncle — her mother’s brother — whom they suspected had been part of the Einsatzgruppen.

“The key factor in identifying the killer in the photo was the availability of comparable images,” says Matthäus. “In this case, I was fortunate to be contacted by a reader of my previous publication on the subject who, along with his wife, suspected that the killer was a relative of hers. He provided photographs of Jakobus Onnen that were close in date to the war and of sufficient quality to allow for facial recognition. The experts involved used both traditional facial recognition techniques and artificial intelligence; the latter produced similarity rates between 98.5% and 99.9%, very high for historical photographs.”

From there, he was able to piece together a biographical profile of the perpetrator: Jakobus Onnen, born into a middle-class family in 1906 in the village of Tichelwarf, near the Dutch border. He was a teacher, spoke French and English, and was an early Nazi: he became a member of the Sturmabteilung (Storm Division, SA) in 1933, the year Hitler came to power, then joined the SS, and during the war, was part of the death squads.

“The photo clearly shows that the killer was a member of the German Security Police and the SD, that is, the part of the police apparatus headed by SS chief Heinrich Himmler, which was part of the infamous Einsatzgruppen,” Matthäus explains. “These units followed the Wehrmacht in its advance through the Soviet Union and killed hundreds of thousands of civilians, especially Jews. After the war, Allied and German prosecutors investigated these murderous units. Onnen’s name was among those identified as members of one of them, but because he died in combat in Ukraine in August 1943, he was never investigated.”

Although there are many images of the Holocaust, only about a dozen capture moments of killings, and all have been thoroughly investigated by historians. The Nazis occasionally took such photos as trophies, though today they appear repulsive and horrifying. For the genocidal Nazi mindset, these were not crimes but the fulfillment of a mission of which they were proud. Many of these images were destroyed after the war, while others surfaced as evidence of history’s greatest crime.

Researcher Wendy Lower published a compelling analysis in 2021 of another piece of evidence: a photograph of a massacre in Ukraine in 1941 in her book The Pit, showing the murder of a mother alongside her child by Ukrainian collaborators. Like The Last Jew of Vinnytsia, she was able to identify the perpetrators, but not the victims.

Matthäus explains: “My colleagues and I tried to locate references to the victim in wartime documents, postwar oral histories, and other sources, but we found nothing substantial. Equally unsuccessful was our attempt to identify him in Soviet photographs taken before the German attack of June 22, 1941, in archives in Ukraine. The conditions for conducting such research in a country that has been under Russian attack for four years are hardly promising; however, they were very helpful. But, once again, the result was negative. I continue to hope that solid leads can be found in the future that will help answer the question of who the man about to be shot was.”

Yad Vashem, the Holocaust museum in Jerusalem and also a research center, maintains a database of 4.7 million names of Shoah victims. About 1.3 million remain unidentified. One of them is still that Jew in Berdychiv, who embodies humanity in one of the most horrifying images in history.

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