[The__]

pawn Code:

CMD:bk(playerid, i, params[])
{
    new fX, fY, fZ;
    if (GetFactionType(playerid) != FACTION_POLICE)
    return SendErrorMessage(playerid, "You are not a police officer.");
    if(ICBK[playerid] == 1) return SendClientMessage(playerid, 0xFF0000AA,"You need to wait 1 minute before calling backup again!");
    SendFactionMessage(PlayerData[playerid][pFaction], COLOR_RADIO, "RADIO: ALL UNITS! %s is requesting immediate assistance, his location has been located on radar! at %s.", ReturnName(playerid, 0), GetLocation(fX, fY, fZ));
    SetPlayerMarkerForPlayer(i, playerid, 0xC2A2DAAA);
    ICBK[playerid] = 1;
    return 1;
}

Not sure why you were running a loop through all players though honestly.