I was mistaken for a criminal and handcuffed.
You want to lock this criminal's hands up so he won't go punching anymore grandpas. You need some handcuffs to make sure he doesn't go around being a criminal anymore. Then you can lock him up good.
This word uses the kun'yomi reading for one kanji and the on'yomi reading for the other. You know them both, so this shouldn't be too hard to remember!