No, this does not.
If monsters change aggro or if the player killing them leaves the map or dies, then you are free to kill the monsters since now the player who had priority is not there. :D
@Ishida: its cool since Jen asked about the @noks debate I figured I would show one of the topics that had some debate dealt with within it.
Edit: Feel free to read our server rules sometime at this link below:
http://pandoraonline.net/forum/showthread.php?tid=1027
Almighty GM-Pandora Wrote:Kill Steal (KS) for Non-MvP Monsters
Do not hit a monsters that "belongs" to another players. Any monster that is attacking/chasing the player, or if the player is also attacking that monster, counts as "belonging" to that player. KS rules do not apply in any public DB room or any GM hosted events unless stated otherwise by the GMs.