Balin's colony was overrun in Moria, they were destroyed by Goblins led by Durin's Bane. Oin was killed by the Watcher in the Water, Ori was killed by some Orc Chieftain (probably Grishlug), Balin was shot by Orc Archers and all the other dwarves were slain by Goblins and the Balrog.