After landing at BOS, uniformed personnel from at least two organisations (state police and customs and border protection) came onto the plane. One person was taken off the plane in handcuffs. Passengers had to stay on the plane for about 1.5 hours after landing. We were told afterwards that an investigation had now been concluded and we were allowed to leave. I have no info as to what actually had happened. I think it was towards the back-left of the plane.