An investigation into police officers' conduct after an anti-Semitic attack in the German city of Bonn has been dropped, authorities confirmed Monday. Professor Yitzhak Yohanan Melamed was mistakenly pinned to the ground and hit in the face by officers, who said they mistook him for the assailant.

Sebastian Buss of the Bonn prosecutors' office said that the tactics were "justified measures under police law."

Melamed, 51, an Israeli citizen who teaches at Johns Hopkins University in the US city of Baltimore, Maryland, was visiting Bonn in July 2018 when a German of Palestinian origin repeatedly knocked the yarmulke from his head.

Police responding to the incident mistook Melamed for the aggressor. They pinned him to the ground and struck him. The officers have claimed they did so after Melamed resisted attempts to subdue him.

The professor, however, has said he was struck dozens of times despite having been "not 100, but 500 percent passive."

Bonn Police Chief Ursula Brohl-Sowa called it "a terrible and regrettable misunderstanding" and apologized to Melamed in person.

Then 20 years old, the assailant was brought to a local psychiatric hospital but was later released. He is still under investigation over the incident.

In Bonn, 2,000 locals held a rally in support of the professor in which men donned yarmulkes and many carried the Israeli and German flags.

On Tuesday, Melamed told the local newspaper Bonner Stadt-Anzeiger: "My only reaction is that, unfortunately, you have a racist and corrupt police system."