Israeli-born architect Eyal Weizman founded his research project, Forensic Architecture, in response to the growing number of civilian conflicts around the world that now take place in cities. "When violence takes place in cities, people die in buildings," he says, "and buildings become evidence." Weizman and his team collect videos, photos, and satellite images as forensic evidence of war crimes. In this short documentary by the Thomson Reuters Foundation, they investigate the origins of violence on "Black Friday," the bloodiest day of the 2014 Israel-Gaza conflict.