In some implementations, the event candidates include audio and/or visual aspects. The event categorizer 3148 categorizes the event candidates into different event categories. The user facing frontend 3150 generates event alerts and facilitates review of the events by a reviewer through a review interface on a client device 220. The user facing frontend also receives user edits on the event categories, user preferences for alerts and event filters, and zone definitions for zones of interest. The event categorizer optionally revises event categorization models and results based on the user edits received by the user facing frontend 3150. The server system 164 also includes a video source data database 509, event categorization models database 510, and event data and event masks database 511. In some implementations, each of these databases is part of the server database 316 e. g. , part of data storage database 3160. The server system 164 receives one or more video streams 504 from the video source 501 and optionally receives event candidate information 502 such as event start information e. g.