Unmasking the Face of Nazi Terror: How Technology Helped Identify a Holocaust Perpetrator

In a remarkable convergence of historical research and modern technology, artificial intelligence has helped solve an 80-year-old mystery surrounding one of the Holocaust’s most haunting photographs. German historian Jürgen Matthäus has successfully identified a Nazi executioner captured in a chilling World War II image, demonstrating how AI can serve as a powerful tool for historical truth rather than deception. The photograph, commonly but incorrectly known as “The Last Jew of Vinnitsa,” shows a bespectacled Nazi soldier aiming a pistol at a kneeling Jewish man beside a mass grave while other SS troops observe the execution. For decades, details about this horrific moment remained obscure—the location misidentified, the date uncertain, and the perpetrator unknown—until persistent historical detective work combined with modern technological analysis finally brought answers.

Through meticulous research, Matthäus determined that this execution actually took place on July 28, 1941, in Berdychiv, Ukraine—not Vinnitsa as previously believed. The killers belonged to Einsatzgruppe C, a mobile Nazi death squad specifically charged with eliminating “Jews and partisans” in newly-occupied Soviet territories. These details came into focus through conventional historical methods, but the breakthrough in identifying the gunman resulted from an unexpected combination of circumstances. After Matthäus’s preliminary findings about the massacre’s correct location circulated in German media, a reader came forward with crucial information: the executioner in the photograph bore a striking resemblance to his wife’s uncle, Jakobus Onnen. This tip provided the historian with a name and biographical details that could be verified against historical records. The open-source journalism group Bellingcat then applied AI-powered facial recognition technology to analyze the resemblance between known photos of Onnen and the man in the execution image. The match percentage was remarkably high, supporting what the circumstantial evidence already suggested—that the gunman was indeed Jakobus Onnen, a German teacher born in 1906 who joined the Nazi party in 1931.

The biography of Onnen that emerged from subsequent research reveals the disturbing trajectory of an educated man who became a willing participant in genocide. Before the war, Onnen taught French, English, and physical education, but his Nazi ideological commitment led him to enlist in the SS Death’s Head Unit at Dachau concentration camp in August 1939, just before World War II began. By 1940, he was serving with the Nazi “Order Police” in occupied Poland, and following the 1941 invasion of the Soviet Union, he joined Einsatzgruppe C—the very unit photographed carrying out mass executions. Under their occupation, nearly all of Berdychiv’s 20,000 Jewish residents were systematically murdered, leaving only fifteen survivors. Despite his apparent dedication to the Nazi cause, Onnen never rose beyond a low rank in the SS hierarchy. His life of violence ended in kind—he was killed in 1943 while fighting against partisan resistance fighters in the Zhytomyr region of Ukraine.

The photograph itself represents a crucial historical artifact that documents the Holocaust’s brutal reality. Unlike images of concentration camp gates or buildings that symbolize the industrial scale of Nazi genocide, this photograph captures the intimate, face-to-face nature of many Holocaust killings. As Matthäus explains, “This image should be just as important as the image of the gate in Auschwitz, because it shows us the hands-on nature, the direct confrontation between killer and person to be killed.” The Einsatzgruppen conducted these mass shootings across Eastern Europe following behind the advancing German army, killing over two million people, primarily Jews. These massacres were not isolated incidents but systematic operations that continued until Nazi forces were driven from occupied territories. The photograph thus serves as visual evidence of how genocide manifested not just in distant gas chambers but in direct, personal acts of murder committed by individuals who made conscious choices to participate.

While the identification of Onnen represents significant progress in understanding this historical atrocity, important work remains unfinished. The Jewish victim kneeling before his executioner still has no name, no recovered identity. For Matthäus, this represents the next challenge in his research—to identify the man whose final moments were so cruelly documented. The historian plans to search Soviet-era records and potentially employ AI technology once again to restore this man’s identity, acknowledging that the victims of Nazi atrocities deserve to be remembered as individuals, not merely as anonymous casualties. This ongoing effort reflects a broader ethical commitment within Holocaust scholarship: to counteract the dehumanization that was central to Nazi ideology by restoring names, faces, and personal histories to those who were targeted for extermination.

The use of artificial intelligence in historical research demonstrates both promising potential and important limitations. Matthäus is careful to emphasize that AI is “not the silver bullet” but rather “one tool among many” in the historian’s toolkit. The technology provided valuable confirmation in this case, but it was the human elements—the tip from a family member, the historian’s contextual knowledge, the meticulous cross-referencing of multiple sources—that made the identification possible. As AI applications become more sophisticated and widespread, this case illustrates a constructive application that serves historical truth rather than undermining it. In an era where deepfakes and AI-generated misinformation raise serious concerns, particularly regarding historical events like the Holocaust that are already subject to denial and distortion, this example shows how the same technologies can instead be harnessed to strengthen our understanding of the past and hold perpetrators accountable, even decades after their crimes.

This remarkable identification process reminds us that history is never completely settled—new technologies, methodologies, and discoveries continue to sharpen our understanding of even the most extensively studied events. The Holocaust, despite being one of history’s most thoroughly documented genocides, still contains countless untold stories and unidentified faces. Each time we recover a name—whether of victim or perpetrator—we add another piece to the historical record and deepen our understanding of how ordinary people became participants in extraordinary evil. By identifying Jakobus Onnen as the executioner in this photograph, Matthäus has demonstrated that the passage of time does not shield perpetrators from identification. Though justice in a conventional sense is impossible for crimes committed eight decades ago by men now long dead, there remains a form of historical accountability in ensuring that their actions are documented, their names recorded, and their victims acknowledged. Through this painstaking work of historical recovery, we honor the memory of those who were killed while ensuring that the mechanisms and individuals responsible for genocide remain visible to present and future generations.