Seems a rather unfortunate situation which shouldn't have escalated this much, however it is what it is.
A human player joined a magmar player's fight. Rather than stay in block, they used things such as Powerful True Arrow to take the loot. As a result, the magmar used a zara hex on them, and so other humans from that clan/alliance started to attack all magmars in the location.
Naturally it will not be the case where one race is slaughtered during hunt, especially when they had no involvement in the issue, hence the wider reaction.
I've omitted the names as they hold no real relevance, but I am sure you can figure out the parties involved (just take a look through completed fights in Ruins)