Things to do in San Francisco

The Christian cult, led by Jim Jones, and later led to a mass suicide/murder in Guyana, had a temple at this location (now an empty lot).
While they were at location Jones orquestrated an event where he had everyone drink wine that he had brought, once he was sure that they were all drinking he told them that it was poisoned and that they would all be dead in an hour.

Three years later nearly 1000 died by poisoned Kool Aid (and automatic weapon fire) in Jonestown, Guayana.