public boolean execute(CommandSender sender, String[] args) {
   if (!(sender instanceof Player)) {
     sender.sendMessage(ChatColor.RED + "This command can only be used as a player");
     return true;
   }
   Player p = (Player) sender;
   PrisonPearlManager manager = PrisonPearlPlugin.getPrisonPearlManager();
   ItemStack is = p.getInventory().getItemInMainHand();
   PrisonPearl pearl = null;
   if (is != null) {
     pearl = manager.getPearlByItemStack(is);
   }
   if (pearl == null) {
     p.sendMessage(ChatColor.RED + "You are not holding a valid ender pearl");
     return true;
   }
   Player imprisoned = pearl.getImprisonedPlayer();
   if (imprisoned == null) {
     p.sendMessage(ChatColor.RED + "The player held in this pearl is not online");
     return true;
   }
   imprisoned.damage(1000000.0); // should be enough
   imprisoned.sendMessage(ChatColor.YELLOW + "You were struck down by your imprisoner");
   p.sendMessage(ChatColor.GREEN + "You killed " + pearl.getImprisonedName());
   return true;
 }