The drawback to the current system is you have to have film on and you may end up with a 20 minute film for 2 mins of action. Having film captured for a set time before and after an event reduces the need to trawl through 'dead time'.
My cctv sysyem works on a similar principle. Everything is recorded but when viewing it skips to events so I do not have to view hours of data.
Perhaps the trick is to retain the record all but only save elements either side of firing a weapon