You'll have to interrogate the second set of Charlie's informants. To reveal their locations, you'll have to wiretap the sectors of the district they're in to reveal their locations. If you already done that beforehand, then they're location (s) will be revealed. This seems to be randomly chosen by the game as well so you should only get one of the two possible targets. The same thing applies to these informants; find them, subdue them, and either kill or recruit them. Once done, they'll reveal the location of Charlie's enforcers in the map.