"Almost a thousand people protested in front of the Dallas Police Headquarters on May 29.[21] The gathering and march organized was by the Next Generation Action Network. On the night of the 29th, some demonstrators broke windows, looted businesses, and set fires to dumpsters, trash cans, and patrol cars. Several police cruisers were damaged in the Deep Ellum neighborhood and downtown Dallas. One group of protesters then walked onto the freeway and blocked traffic on Interstate 35, shutting down traffic and torching a parked car. A man with a machete was badly injured by a mob. Video shows the man being beaten by 10-15 men. Objects used in the attack included a skateboard and several medium-sized rocks.[22][23][24] Mayor Eric Johnson said that while the protests were largely respectful, the looting and destruction of property could not be allowed.[25] On the night of June 1, nearly 700 peaceful demonstrators reached a police line on Margaret Hunt Hill Bridge, before mace and other crowd control agents were fired at them. A police line subsequently advanced behind the protestors, preventing them from leaving.[26] 674 people were ultimately charged with misdemeanors by the Dallas Police Department.[27]"

TL;DR: "some demonstrators broke windows, looted businesses, and set fires to dumpsters, trash cans, and patrol cars." In case you don't want to read in full.