public OnPlayerTakeDamage(playerid, issuerid, Float: amount, weaponid)
{
    if(issuerid != INVALID_PLAYER_ID) // If not self-inflicted
    {
        new
            infoString[128],
            weaponName[24],
            victimName[MAX_PLAYER_NAME],
            attackerName[MAX_PLAYER_NAME];
 
        GetPlayerName(playerid, victimName, sizeof (victimName));
        GetPlayerName(issuerid, attackerName, sizeof (attackerName));
 
        GetWeaponName(weaponid, weaponName, sizeof (weaponName));
 
        format(infoString, sizeof(infoString), "%s has made %.0f damage to %s, weapon: %s", attackerName, amount, victimName, weaponName);
        SendClientMessageToAll(-1, infoString);
    }
    return 1;
}

public OnPlayerTakeDamage(playerid, issuerid, Float: amount, weaponid)
{
    if(issuerid != INVALID_PLAYER_ID && weaponid == 34)
    {
        // One shot to kill with sniper rifle
        SetPlayerHealth(playerid, 0.0);
    }
    return 1;
}