The Astor Place Riots

"One of the worst disasters in the history of the theatre took place May 10, 1849 at the Astor Place Opera House. Two of the most famous stars of the day, American Edwin Forrest (above) and "the eminent tragedian, " Englishman William Charles Macready, were announced to play Macbeth on the same night. A professional feud, fueled by jingoism erupted into a scene of violence not seen before or since in the annals of the theatre. When the smoke cleared, twenty men lay dead, and the theatre destroyed."

via: metafilter