「くっ!!」 as a remark of surprise?

Precursor: [When I first arrived in Osaka in November, let's just say for various reasons, I was unable to secure a place to stay for some time, so I hung out in various public areas, away from other people, to not get in the way. One of the places I stayed at during the day in order to get wifi was a sort of tunnel connecting a shopping mall to a train station, I believe. I stayed in a large square cutout section in the wall next to the door, hope that can be visualized, which is necessary to understand the situation.]
Most people came through the doors, passing by, and didn't notice me, some did and just looked and kept walking/talking like normal. But then a person walked through the doors (I think with friends) and as soon as he looked at me he said 「くっ！」, of course walking past afterwards.
At first, I thought this was an unfinished word, like maybe he was trying to say 「臭っ」 and stopped when he realized there was a person there (I don't think I smelled that bad especially for someone to notice from a distance though). But then eventually, after a few more people came through, another person (I think who was alone this time) made the same remark upon looking at me, 「くっ！！」. Now at that point, I was deeply pondering what such a remark could mean, but I can only assume that they were surprised at seeing someone sitting in the corner on the floor. Is it possible that this is a remark of surprise? Is it something else? I think about moments like these often, and I still can't guarantee to myself that it was an expression of surprise because I can't find anything on such a small expression, and that day contained the only two times I've heard it. I don't doubt my ability to recognize singular mora pronunciations, but at this point I can't even be sure that I heard them correctly because that's how little info I could find... What do you guys think? Thanks

I was going to guess they may have said クソ used in the sense of "w t f." But I don't have much expertise in the use of クソ and I'm not positive it's used that way.

It seems to me that you misheard it. My wild guess is びっくり（した）.

mdchachi said:

I was going to guess they may have said クソ used in the sense of "w t f." But I don't have much expertise in the use of クソ and I'm not positive it's used that way.

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I won't rule it out

Toritoribe said:

It seems to me that you misheard it. My wild guess is びっくり（した）.

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Even if I did mishear it, I find it highly unlikely that I missed multiple mora... But because it's been so long since then, I won't rule that out either...
I've heard people say びっくりした before and even though it's usually said fast (out of shock), I have been able to catch it for quite a while (since almost a year ago). If I misheard the one mora as the wrong phoneme, that's one thing, but I would be shocked if multiple mora went unheard... Even when I tried to talk to a guy that kept ending his sentences in whispers, I could at least tell that he was still saying more mora (I don't even know if that's the right way to word it buttt)

びっくり can be uttered as っくり as an interjection.

Toritoribe said:

びっくり can be uttered as っくり as an interjection.

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Well if that's the case I guess it's entirely possible that I misheard...This does seem to be the most valid explanation for now. Thanks