They became popular throughout mainland Europe in the 17th and 18th centuries, sometimes with fatal results. In 1792 Gustav III of Sweden was assassinated at a masquerade ball by the disgruntled nobleman Jacob Johan Anckarström, an event which Eugène Scribe and Daniel Auber turned into the opera "Gustave III". The same event was the basis of Giuseppe Verdi's opera "A Masked Ball", although the censors in the original production forced him to portray it as a fictional story set in Boston. Most masks came from countries like Switzerland and Italy.