On November 27, 1978, San Francisco mayor George Moscone was fatally shot in his City Hall office by a disgruntled city supervisor. An openly gay official, Harvey Milk, was also slain that day. The perpetrator, a conservative, homophobic former police officer, Dan White, objected to the citywide reforms that the Moscone Administration had implemented since 1975. Mayor Moscone was a Democrat and well-liked former state senator who altered the municipal election process, which forced candidates to the San Francisco Board of Supervisors to be far more involved in the neighborhoods they sought to represent. Milk, an activist from the Castro Street area, became the city's first openly gay elected official.

Just a few days before the City Hall shootings, 911 members of Jim Jones's People's Temple had committed suicide in Guyana. The cult was originally based in San Francisco, and some of its members had worked for Moscone's mayoral campaign. The event shocked the city, and to conservatives like Dan White, it symbolized the unwholesomeness of Moscone's liberal politics. White had quit his supervisor post a few weeks earlier but came to Moscone on November 27 to request reinstatement.

During his 1979 trial, White's lawyers claimed that he was addicted to junk food and was mentally incapacitated because of it at the time, which was mocked as the "Twinkie Defense." He was convicted of manslaughter, which angered the gay community in the city to the point of riot. Paroled in 1984, White committed suicide a year later.