Automatic Event Extraction from texts emerges as an im- portant and complex text mining task. Its goal is to detect description of events of a speci¯c type described in the text. For each event the Event Extraction system is expected to ¯nd the time, the location, the participants in this event and their roles, as well as other related circum- stances. In this talk we present a Machine Learning approach for learning of information extraction patterns, a method for semi-automatic lexical acquisition, and an information aggregation strategy implemented in a working prototype nexus which detects automatically security related events in clusters of news articles.