Integrating security in the development and operation of information systems is the cornerstone of SecDevOps. From an operational perspective, one of the key activities for achieving such an integration is the detection of incidents (such as intrusions), especially in an automated manner. However, one of the stumbling blocks of an automated approach to intrusion detection is the management of the large volume of information typically produced by this type of solution. Existing works on the topic have concentrated on the reduction of volume by increasing the precision of the detection approach, thus lowering the rate of false alarms. However, another less explored possibility is to reduce the volume of evidence gathered for each alarm raised. This chapter explores the concept of intrusion detection from the angle of complex event processing. It provides a formalization of the notion of pattern matching in a sequence of events produced by an arbitrary system, by framing the task as a runtime monitoring problem. It then focuses on the topic of incident reporting and proposes a technique to automatically extract relevant elements of a stream that explain the occurrence of an intrusion. These relevant elements generally amount to a small fraction of all the data ingested for an alarm to be triggered and thus help reduce the volume of evidence that needs to be examined by manual means. The approach is experimentally evaluated on a proof-of-concept implementation of these principles.