Ok, for instance, in the chapter "A friend", which is about chapter 6 I think, I could be totally wrong on that but anyways there are some locked lockers just before a fairly large guard outpost. If you listen to the guard conversation, the one says to the other that "If you're here no one is watching your stash", which I assumed is the three lockers just before them (A picture of a lock does show up when you hover over them) to which the other guard replies "It doesn't matter, I have the only key". I killed all the guards but there is no key to be found anywhere. I scoured the relatively small area for literally an hour. Shining my flashlight in every crevice, jumping on any structure I could to get to any weird angles I could, no key. I haven't even played anymore because I don't want to skip it, but I cannot fine a single walkthrough, video or text based, that shows how to unlock them. 90% of the video walkthroughs I checked out, the person playing didn't even bother to look at said lockers. So I'll be waiting.
I dont know about the locked things but I do know that the guard who talks about his stash will open his locker after he answers the intercom and you can nab the gun there (its a nearly fully modded semi auto pistol).
There is no overkill, there is "Open Fire" And "I have to reload". Gamertag: Fallout10mm