Symbols next to mob names

[dragonsi]

OK, here's one my son asked me yesterday and I had no answer for him: What do the letters in blocks (for example a K in a block) mean to the right of mob names?

Actually, these symbols did not originally appear on the mob when it first spawned. Here is what happened:

Someone came along (before you arrived) and either attacked a mob or was aggroed by it, but that mob had a LINKING mob, or 2 mobs, to it. So now this player is being attacked by either 2 or 3 mobs. He either dies or runs away and the mobs chase him but eventually reset to their starting position again. You come along and NOW see [K] at the end of the name and 2 more letters on 2 other mobs. That will indicate to you those are linking mobs and you were not the first to attack them either.