From Multi Theft Auto: Wiki
This event is triggered when a player has been muted by setPlayerMuted.
The source of this event is the player who got muted.
If this event is canceled, the player will not be muted.
function muted() outputChatBox(getPlayerName(source) .. " has been muted.", root, 255, 0, 0) end addEventHandler("onPlayerMute", root, muted)