Well. The only set of folks who can routinely kill fellow citizens with or without cause and get away with it, and when 20 of them surrounded you in a closed space, and you cannot walk out of that place, I think it is normal to be afraid of.

But, I didn't feel like carrying a gun or something else to protect me, I just wanted to stay out of that place.

To me it is not paranoid. A reasonable cautious approach.
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A little paranoid? No this is get out the prescription pad.

Any person, in the United States, in a situation where he is surrounded by a massive police presence on a transportation platform, and is paranoid about the police shooting him, is really in a really bad place mentally.

A sane person is very very concerned, they would figure there is a reason all the police were there and that there was some threat they shoud be really alarmed about.

The cops are going to shoot me, because they may think my bubble gum is a weapon if I reach in my pocket, is paranoid beyond anything normal.