Ziemann died Thursday of pancreatic cancer at a monastery in Arizona, said his brother, Joe.
The bishop gave up his post at the Diocese of Santa Rosa after a priest filed a lawsuit alleging that Ziemann had coerced him into a two-year sexual relationship in exchange for keeping silent about the priest's admitted theft of money from a Ukiah parish.
Ziemann publicly acknowledged his affair with Father Jorge Hume Salas after the lawsuit was filed but said the relationship was consensual.
The Santa Rosa Police Department and the Sonoma County district attorney's office investigated Salas' allegations of sexual coercion, bolstered by a secret tape-recording of Ziemann apologizing to the priest.
Authorities declined to file criminal charges, however, questioning Salas' credibility. Their investigation showed that Salas had been expelled from several seminaries and posed as a priest before he was ordained.
The Santa Rosa diocese agreed to a $535,000 settlement with Salas, who has since left the priesthood and returned to his native Costa Rica.
Church leaders, meanwhile, found Ziemann had squandered $16 million in diocese money -- the result of poor oversight, bad investments and overspending, diocese officials said.
The shortfall forced the diocese to lay off about a third of its staff and cut funding for religious education, youth ministry and other programs, angering many local Catholics who had contributed money, the officials said.
Diocese leaders said Ziemann did not personally benefit from his financial decisions.
Ziemann later apologized for the turmoil. In a letter read on his behalf at services throughout the diocese after his resignation, he wrote: "I acknowledge with deep regret my responsibility for the current state of affairs, about which you are justly angry. I cannot express to you enough the deep remorse and repentance I feel for letting you down."
Ziemann's legacy continues to reverberate across the diocese of 150,000, the diocese's spokeswoman said.
"It undermined . . . trust in the church," said Deirdre Frontczak, the spokeswoman and professor of business communications at Santa Clara University. "Many people stopped going to church [and] still have never come back."
Still, Frontczak and others said they hoped Ziemann would also be remembered as an inspiring, if flawed, leader. To many, he was simply "Bishop Pat," known for his charisma, spirituality and an ability to motivate young people.
One close friend said the experiences that ended Ziemann's seven-year tenure in Santa Rosa changed him. "He is the first one to say, 'I violated my vows,' " said Joe Piasta II, the bishop's onetime attorney who visited him in Arizona shortly before his death. "The whole crisis made him very human."
Ziemann grew up in Pasadena, the third of eight children born into a devout family. His grandfather, Joseph Scott, was a well-known defense attorney, and his father, J. Howard Ziemann, was a Los Angeles County Superior Court judge and dean of Loyola Law School. Two of his uncles were diocesan priests in the Los Angeles area; he was named after them -- George Patrick.
Ziemann seemed destined for the priesthood at an early age, said his brother, Joe.
"I don't think there was ever a doubt where Pat was headed," Joe Ziemann said. "He always seemed to fit right in with the priesthood."
Ziemann was ordained in 1967 in the Archdiocese of Los Angeles, where he worked as a parish priest, high school teacher and dean and vice rector at Our Lady Queen of Angels high school seminary in the San Fernando Valley. He was appointed auxiliary bishop of the Los Angeles archdiocese in 1987 and named bishop of Santa Rosa five years later.
Ziemann's family did not speak publicly about his troubles at the time, but Joe Ziemann lamented recently that the problems had come to define his brother's legacy.
"We knew Pat long before the '99 incident or whatever it was," he said. "There are just too many years before and after when so much good was done. We'll let the judgment of that take place on the other side of the veil."
Even as Ziemann began life anew in 2000 at Holy Trinity Monastery in Arizona, however, he faced fresh allegations of alleged misconduct related to his time in the Los Angeles archdiocese.
He was named in two lawsuits that accused him of molesting three boys. The archdiocese settled the claims for $2.8 million, according to plaintiffs' attorneys. Ziemann adamantly denied the charges, said his former attorney. A Los Angeles archdiocese spokesman declined to comment on the litigation.
At the monastery near Tucson, Ziemann prayed in the chapel, although he did not lead Mass. And he worked in the kitchen. The monastery's superior, Father Henri Capdeville, said he never asked Ziemann about his past but instead tried to provide a sanctuary for the bishop to deepen his spirituality.
"I know he did some wrong in Santa Rosa," Capdeville said. "But he did his time at the monastery. He did some reparations for the harms he did in the best way he could."
In addition to his brother Joe, Ziemann is survived by four brothers and a sister.