Police at the beginning
They had no reason to hassle him. He had no part in the robbery, and both the victim and witness said he wasn't involved. They wouldn't detain him like that, and they had no business in his business.
shareThe only unrealistic thing was handcuffing him and sticking him in the van cage.
They detained him because he wasn't making sense, so they believe he was either under the influence or mentally ill and we're concerned about him. Both are legitimate reasons for detainment/further questioning as far as the law is concerned.
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When logic and science aren't on your side, you always lose.