The problems started following an allegedly rigged election earlier in the year. An Irish-Catholic politician named James P. Casey managed to get a seat on the city board of supervisors.

A campaigning local newspaper editor James King, of the Daily Evening Bulletin, accused Casey of being part of a criminal gang.

On May 14, 1856, Casey confronted King in the street and shot him dead with a Colt navy revolver.

The vigilante committee was formed at this point.

A crowd of 500 vigilantes then surrounded the local jail and removed Casey who was put on a short trial and then hanged.

Critics say that this vigilante committee was an attempt for the native born, Protestant elite, to regain political control of the city. Whatever the motivation, the second committee was disbanded later in 1856, after having executed a number of people.