Where does Trump's remark "When the looting starts, the shooting starts" come from?

In order to better understand the origin and background of this quote, we ask Prof. Lora Anne Viola of the John F. Kennedy Institute of the Free University of Berlin for a more precise classification. Trump's statement actually refers back to the words of a police commissioner in 1967.

ARD, maischberger.die woche, 3.06.2020

Translated with www.DeepL.com/Translator (free version)