public OnPluginStart()
{
   HookEvent("player_death", Event_PlayerDeath)
}

public Event_PlayerDeath(Handle:event, const String:name[], bool:dontBroadcast)
{
   new victim_id = GetEventInt(event, "userid")
   new attacker_id = GetEventInt(event, "attacker")

   new victim = GetClientOfUserId(victim_id)
   new attacker = GetClientOfUserId(attacker_id)

   /* CODE */
}