Whether innocent or guilty, whether BK thought LE might be after him or not, I think that LE breaking in like that (and it would have been a sudden, coordinated and LOUD break-in) would have scared him and his flight response apparently kicked in immediately and he ran for any safety he could. The three most expected responses to this type of sudden stimulus are fight, flight or freeze. His was a classic example of a flight response. The response is a completely involuntary response by the autonomic nervous system and he could not have controlled himself or done anything different.
Fight, flight, or freeze response: Signs, causes, and recovery.
I'm aware of the biology of fear and it's one of my favorite topics. These days, most scientists would say that there are more than three responses. My point wasn't about whether he was adrenalized/panicked/slightly afraid/very afraid or anything like that. I would have thought he was living in a state of anxiety - less severe if he was innocent, more severe if he is not, but with him
aware that he could be/probably was a suspect.
You said you thought he was surprised in the way similar to what any of us would feel if we were caught by people breaking in, in the middle of the night (I may have misunderstood you). I said I thought he was probably already nervous. You could be right - he might have had no clue that he was being surveilled by cops outside his house almost from the time he arrived home. He might never have pondered whether his own white Elantra was on some kind of list. It's entirely possible.
I do think that people with a background in law or criminal studies tend to have minds that go in "what if" directions, including "What if people think I did it?"
Here's an article (unfortunately only part of it is free) that posits four different responses (the fourth one is lie/dissemble)
Researchers found that genetics influenced which response was going to be used. Interestingly, in situations where groups of people were confronted by a real threat, all four have been observed. Panicked bargaining and pleading is a potential fifth (and there are parallels in non-human animal behavior, which is important - because the biochemistry of this is central to understanding it). Note that in humans, there seems to be a suggestion that we can use pretense/acting as a bucket category for "submit," "negotiate" and "lie." Many of us have seen this in action.
Genetic and neurochemical research has found specific biomarkers corresponding to the biological state "freeze" (it's a fascinating topic). And very different ones (but related) associated to "flight." And "freeze" is usually held to be a kind of setting in between "fight" and "flight" (in terms of biochemistry).
This is a proposed fifth response that says "submit" is another choice:
Background Catatonia is a severe psychomotor disorder that presents as abnormality of movement which may also be excessive or severely slowed. It often inhibits communication when protracted or severe. In this study we investigated the emotive and cognitive experience of patients with catatonia...
link.springer.com
Naturally, there are different rubrics for what separates "freeze" from "submit" (but the biochemistry seems to indicate there are more states than just two or three).
Also, it's clear that culture mediates all this in humans. Some cultures are more prone to one set of these, and so on. Many cultures deliberately terrify their offspring as they grow up, in order to observe and train these responses, reshaping them (the Hopi are particularly interesting in this regard). People who undergo military or police training actually modify their biochemistry so that their responses are different. So do people who study martial arts (that's one of the main points). Deliberately scary activities are part of basic training, military training, scuba diving, etc. People who do these things modify their responses.
Studying grim stuff sometimes induces a change in all these responses. There are doctors and nurses who (embarrassing to themselves) passed out at some point in their early training, and revived, got up and continued onward - again and again in some cases. The body learns to modify the response. Repeated exposure to scary situations is basically how it's done.
In this case, BK has a "safe space" that just happened to have a weapon in it, which was of course a strong possibility in this case, hence the form of arrest we saw. IMO. People make "safe spaces" with weapons in them all the time. LE always errs in the direction of just acting as if that's the case and that the suspect may make a run for that safe space (make a stand). I have no clue if that report of Kohberger darting downstairs is backed up by strong evidence or not. Can't even remember where it was reported.
My point is that I simply can't believe it wasn't in the back of his mind (and that's of course IMO).