Let me try to help you out with your reading comprehension problem. In the text below, which is in bold, you can see all he did was shout "what did you do to her" and he was arrested. Since when is raising one's voice grounds to be immediately handcuffed and arrested?
Of course when I say she "told me later," it’s because she wasn’t able to tell me at the time, because as soon as I demanded to know what the federal employee had done to make her cry, I was swarmed by Portland police officers. Instantly. Three of them, cinching my arms, locking me in handcuffs, and telling me I was under arrest.