 Members of the Azusa 13 gang, associated with the Mexican Mafia, were indicted in 2011 for harassing and intimidating black people in Southern California.Gang-related activity and violence has increased along the U.S. Southwest border region, as US-based gangs act as enforcers for Mexican drug cartels.A gang war is a type of small war that occurs when two gangs end up in a feud over territory.