About 40 people gathered on July 16 to protest George Zimmerman's acquittal in the Trayvon Martin death, but it turned into a crime spree.
LAPD officials say there were 11 incidents that night, including 10 robberies and one act of vandalism.
A similar scene played out in the Crenshaw District the night before with people jumping on cars and vandalizing private property.
"It's unacceptable what happened in Southwest and in Hollywood. In light of what the good people that were up there for lawful purpose intended to do, it really put a black eye on those days, and we can't have that," said LAPD Det. Kirk Albanese.
In Hollywood, it amounted to approximately $1,700 being taken in cellphones and cash from businesses and individuals. Property damage was estimated at $300.
Twelve people -- 11 of them juveniles -- were arrested for the Hollywood crime spree, but police say more arrests are likely. Detectives are looking for one person in particular who was caught on surveillance video on Hollywood Boulevard. Officials say he ran into Skooby's Hot Dogs and took off with the tip jar.
"If community members were out there, tourists or people that live and frequent Hollywood, and they have cellphone video or stills depicting what occurred out there on the 16th of July, Hollywood detectives want that information," said Albanese.
Authorities reminded parents to be vigilant about what their children are doing on social media. Criminal activity, such as inciting riots and mob activity on Facebook or Twitter, will be investigated thoroughly by the department and prosecuted by the D.A., police said.
Anyone with information, pictures or videos from that night is urged to call the Los Angeles Regional Crime Stoppers at (800) 222-TIPS.