bash mob 

"Bash mob" is a term used to describe the disturbing new trend beginning in the year 2011 for people to assemble suddenly in a public place to attack innocent people, then disperse. "Bash mobs" are organized via telecommunications, social media, or viral e-mails, similiar to "flash mobs." Bash mobs are similar to flash mobs, except bash mobs are violent, causing innocent people to be injured or killed and also in the mayhem sometimes causing property damage . . . . . . . {A "flash mob" is a group of people who assemble suddenly in a public place, perform an unusual and sometimes seemingly pointless act for a brief time, then disperse, often for the purposes of entertainment and/or satire. Flash mobs are organized via telecommunications, social media, or viral e-mails. The term "flash mob", coined in 2003, is generally not applied to events and performances organized for the purposes of politics (such as protests), commercial advertisement, publicity stunts that involve public relation firms, or paid professionals}.

News reporter: "There has been an increase in bash mobs recently and the Chicago Police are working hard to stop this trend."

bash mob by demographic-man December 12, 2011