Shortly after Summoning was released, a player who had gone to the Varrock or Port Sarim Rat Pits would challenge a player, then disconnect or log out quickly after the cat would attack another player's cat or a rat. Then, they would quickly log back in, spawn outside that area's Rat Pits and then their cat would attack any other player's cat that was in its vicinity. It would also attack summoning familiars. If the familiar killed was carrying items, the player could pick up the items.
The massacre went on from Port Sarim, to Falador, to Taverley, then the player teleported to Varrock, met his friends, and then finally ended in Canifis when a Jagex Moderator disconnected the players and a system update followed. The players were not banned for this, but received rollbacks on their accounts. This was also dubbed the World 97 Massacre.