The woman whose suicidal rampage at a Santa Barbara County postal facility killed seven people believed that she was threatened by a conspiracy involving its workers, authorities said.

Jennifer San Marco left writings at her New Mexico desert home alluding to a vague plot involving the Goleta mail-sorting plant where she once worked, a local medical facility and the Santa Barbara County Sheriff's Department, sheriff's Sgt. Erik Raney said in a telephone interview Friday.

"There was several different writings that were described to me as kind of just ramblings, not anything specific, but they alluded to a conspiracy," he said.

"She obviously felt that the post office was out to get her in one way or another," Raney said. "That establishes as good of a motive (for the killings) as we can determine at this point."

Raney said that despite a history of mental illness, San Marco managed to buy the gun and ammunition used in Monday night's killings from two New Mexico pawn shops.

Gun purchase went unquestioned

She bought the 15-round, 9 mm Smith & Wesson model 915 last August from a pawn shop in Grants, N.M., and an unspecified amount of ammunition from a pawn shop in Gallup, N.M., Raney said.

How she managed to purchase it is "the million-dollar question yet," he said.

Paul Castillo, owner of Ace Pawn and Antiques, told the Santa Barbara News-Press that San Marco bought the gun for $325 without saying why she needed the weapon.

She filled out an application for a background check, which didn't turn up any problems, and picked up the gun two days later, Castillo said.

The gun originally was purchased by another person in San Jose and later sold to the pawn shop, Raney said.

The last victim to die in the rampage was the first buried Friday.

More than 1,200 mourners overflowed a church for the funeral Mass for Charlotte Colton, a mother of three who was shot in the head and died Wednesday at a hospital.

"If there was anything she did it, was love boldly and fearlessly," Colton's niece, Katrina Baggao de la Cruz, told mourners at St. Raphael's Catholic Church, the News-Press reported. "You simply wanted to be a better person around her."

Colton, 44, of Santa Barbara, was survived by her husband, Jim, and three sons. She was buried at Calvary Cemetery.

Psychiatric history

San Marco, 44, worked at the Goleta postal facility for about six years before she was placed on retirement disability for psychological reasons in 2003, the Postal Service has said.

Employees said her behavior was increasingly more bizarre and that she sometimes talked or argued with herself or made racist comments, although she never made any threats to them.

In February 2001, deputies were called to remove her from the plant because of strange behavior.

She was sent to a Ventura psychiatric hospital for three days of assessment but Raney said he did not know the diagnosis. The hospital was not the medical facility mentioned in San Marco's writings, Raney said. He declined to identify the facility named in the writings.

"It might have just been a place where she had her regular doctor's visits," he said.

The 2001 incident may have prompted her to place the Sheriff's Department in her conspiracy but it was unclear whether the incident specifically motivated the killing spree, Raney said.

Search for clues

"Was this cognitive thought? Did she have a specific grudge for a specific reason and came back with a vendetta in mind, or (was it) a manifestation of her psychosis? ... I don't know that we'll ever know that," he said.

Also found in the woman's home was a check for cash with the notation "will," indicating San Marco left a will, "and that may shed more light on what's happened here," Raney said.

Police in New Mexico say San Marco, who was white, distributed a publication called "The Racist Press." The newsletter included error-laden explanations of various religions and a confusing theory linking the U.S. government to "Son of Sam" killer David Berkowitz, the Ku Klux Klan and racist murders.

Authorities believe that San Marco drove from New Mexico to California last week. On Monday night, she sneaked into a Santa Barbara condominium and shot to death her first victim, a woman who had been her neighbor several years ago and with whom she had argued.

Less than an hour later, San Marco began her rampage at the postal plant.