Playback Pre-Recorded Video

I’m a total noob to both media streaming and EvoStream, so bear with me. I’m not sure what the correct terminology is, but here is my scenario: I will be pulling (and recording) streams from surveillance cameras. When requested by a user, I want to be able to send pre-recorded video to the user for a specific time-period in the past. For example, say a store is robbed at 10:00pm and the police aren’t notified by the store owner until 15 minutes later when the perp runs away with the loot. 😯 What the police are going to want to view from our application is the recorded video from 09:50 – 10:15, for example. I have absolutely no idea how to even start to go about doing this. I’ve started messing around with recording streams, but I don’t know if I’m doing it correctly and/or doing it in such a way that I can easily provide pre-recorded "slices" of video to the user. And how to go about providing that pre-recorded video to the user is a mystery to me too. If someone could explain the methodology that would work for this scenario, I’d really appreciate it. Thanks! ~~Bonnie