The woman who was found shot shot to death in Tiburon yesterday morning, making it the city's first homicide in a decade, has been identified as 75-year-old Joan Rosenthal. According to police, there was no sign of a break in and nothing from Rosenthal's residence was stolen. Rosenthal, described as a "a wonderful member of the community," held a "a contemporary fiction book group with Tiburon Mayor Alice Fredericks since 1997." Anyone with information as to who did this should call the Marin County Sheriff's Department at 415-499-7265.