A security system can have a Multimedia Data Stream management system that receives the stream of videos captures or stream of frames, and has a relation (i.e. a table) with images of WANTED criminals, and another relation with images of weapons. Then one can pre-design couple of useful Continuous Queries CQs such as:

Tell me whenever you see an object similar to any weapon.

Tell me whenever you see a WANTED person.

Tell me whenever an object (or more) in several frames within the last 30 seconds moves in a very "violent" manner.

If any of the above, start recording the video on a "threat" clip for future reference.

Thus, if the guard missed anything, or had to leave his place for whatever reason, the system can help him.