Toward the end of his speech he was interrupted by a delegation of police who arrived headed by police captain John Bonfield who ordered the meeting to disperse. Fielden briefly protested before he stepped down from the wagon on which he had been speaking. At that moment, someone threw a bomb which exploded in the midst of the crowd. Fielden was shot and slightly wounded in the knee as he fled in the resulting chaos (he was the only Haymarket defendant to be wounded). After he had the wound dressed he returned home. He was arrested the following day and charged with conspiracy in the bombing.