San Marco was born on December 6, 1961 and worked for the United States Postal Service at the Goleta mail processing and distribution centre in Santa Barbara County. She was removed from the job in 2003 after episodes at work, and was taken from the building by police on one occasion; she was later placed on medical retirement for psychiatric reasons. She moved to New Mexico, where she attempted to start a newspaper and was known to local officials as unwell.
On January 30, 2006 she returned to Goleta. She shot Beverly Graham, fifty-four, a former neighbour, at Graham's condominium, then drove to the mail plant, followed an employee's car through the security gate, and shot six people inside: Ze Fairchild, thirty-seven; Maleka Higgins, twenty-eight; Nicola Grant, forty-two; Guadalupe Swartz, fifty-two; Dexter Shannon, fifty-seven; and Charlotte Colton, forty-four. She then shot herself.
Seven dead, plus the shooter. It is the deadliest shooting at a United States workplace committed by a woman, and it is a mass killing, not a serial one; it belongs in this archive under that classification.
The subsequent reporting concentrated on the two years between her removal from the plant and the shooting: she had been the subject of workplace incident reports, a police removal and a psychiatric retirement, and had bought the pistol legally in New Mexico in 2005. No inquiry found a point at which the purchase could lawfully have been prevented.