We present simulator of alerts for the Large Synoptic Survey Telescope (LSST) developed by Belgrade group. This simulator will be used in testing the functionality of external event brokers/Complex Event Processing (CEP) engines. It is based on current LSST Simulation framework and allows for different classes of objects to be ‘alerted’. A Web service based on our simulator is prototyped and can be accessed by developers of brokers/CEP engines.