Tsume's pack was a wolf pack that was destroyed for unexplained reasons, though, presumably, by Nobles due to the manner of its destruction. Tsume, being younger in the flashback than in later episodes, explains that he ran. He says the leaders and survivors of the pack saw his cowardice and exiled him. Along with the exile, he was bitten and thrown down by a higher ranking wolf, leaving him with a scar on his chest.