SAN FRANCISCO (CBS SF) -- San Francisco Mayor Ed Lee, who became the city's first Asian-American mayor when he was named to serve out the remainder of Gavin Newsom's term in Jan. 2011, died suddenly early Tuesday morning, city officials said.
He was 65.
In accordance with the City Charter, Board of Supervisors President London Breed became Acting Mayor of San Francisco, effective immediately. Breed becomes San Francisco's first female African American mayor in any capacity.
In a short news release, officials said Lee passed away on Tuesday, December 12 at 1:11 a.m. at Zuckerberg San Francisco General Hospital. Family, friends and colleagues were at his side.
"Mayor Lee arrived shortly after 10 p.m. He was in critical condition," said Dr. Susan Ehrlich, the chief executive officer at Zuckerberg San Francisco General Hospital. "We attempted life-saving measures for several hours. He died at 1:11 am in the morning...We expect medical examiner to determine the case of death."
At a morning news conference, Breed said the city has suffered a major loss.
"He was from the dawn of his career an advocate for the powerless, a voice for overlooked," she said of Lee. "Someone who fought for those in need before himself. That commitment to others defined the mayor's three decades of public service."
She ordered flags to be at half staff for the next 30 days. All public transit in Oakland, San Jose and San Francisco -- BART, VTA, AC Transit and San Francisco Muni -- stopped service for a minute or two at noon for a moment of silence in Lee's memory.
Former San Francisco Mayor Willie Brown, a close personal friend of Lee's, said the mayor was shopping at the Diamond Heights Safeway when he suffered a heart attack. He collapsed and was rushed to the hospital.
"(Lee's wife) Anita sent him to do his family chores," Brown said. "He never moved away from being a husband and a father as a mayor."
His death was announced by officials early Tuesday.
"It is with profound sadness and terrible grief that we confirm that Mayor Edwin M. Lee passed away," the statement read. "Our thoughts and prayers are with his wife Anita, his two daughters, Brianna and Tania, and his family."
Lee was appointed as mayor by the Board of Supervisors on January 11, 2011 after Newsom resigned to become Lieutenant Governor. He won election on Nov. 8, 2011 and was re-elected in 2015.
WATCH: The Career Of San Francisco Mayor Ed Lee
Lee was among four candidates to replace Newsom, but initially said he was not interested in the job. At the urging of Brown, the late Chinatown power broker Rose Pak and Sen. Dianne Feinstein, he tossed his name into the selection process.
"Those of us who helped orchestrate his selection as interim mayor knew he was going to be an important figure," Brown told KPIX 5. "He clearly was important in the symbolism of the mayorship. His being the first person of Asian descent in a major American city in this nation was in and of itself decisive."
As he talked about Lee, who was head of purchasing and public works for the city when Brown was mayor, his voice cracked with emotion.
"I don't know San Francisco without Ed Lee," Brown said. "He was a part of everything. He was the human rights director. He was head of purchasing during my administration. He was head of public works. He became the CAO (chief administrative officer) for the city... I just can't imagine the city without Ed Lee."
WATCH: Former Mayor Willie Brown on Lee's Death
Feinstein called it "sad day for San Francisco."
"Early this morning I learned of Ed Lee's death," Feinstein said in a statement. "It's a very sad day for San Francisco and all of us who knew Ed. My thoughts turn to all of Ed's family, especially Anita, Brianna and Tania. I know what this is like and wish I could give Anita a hug and express my sorrow."
"Ed was an excellent mayor of a great but sometimes challenging city. His equanimity and quiet management style was effective and allowed him to solve problems as they occurred," she continued. "My heart and thoughts are with Ed's family and friends and the city I love."
New York City Mayor Bill de Blasio took to Twitter to offer his condolences.
"Deeply saddened to hear of the death of Mayor Ed Lee," de Blasio wrote. "He was a good friend and a tireless fighter for the people of San Francisco. Our thoughts are with his family."
Senator Kamala Harris also was stunned by Lee's death.
"I am deeply saddened by the passing of my friend, San Francisco Mayor Ed Lee," she wrote on Twitter. "He was a fierce advocate for civil rights and worked tirelessly for workers' rights and his leadership will be missed. Keeping the mayor's family in my prayers during this difficult time."
San Jose Mayor Sam Liccardo added his condolences.
"A dear friend & colleague @mayoredlee has left us too early," he tweeted. "Ed was a good and incredibly gracious man, at a time when goodness, graciousness, and civility are not sufficiently valued in public life. My heart goes out to Ed's family, Anita, Tania, & Brianna."
WATCH: Supervisor Jane Kim On What It Meant For San Francisco To Have An Asian American mayor
Over the last year, Lee has been at loggerheads with President Donald Trump over immigration. San Francisco, under Lee, has been a leader among American cities in the Sanctuary City movement.
Recently, Trump focused his ire at Lee and San Francisco after a local jury found Jose Ines Garcia Zarate -- an illegal immigrant -- not guilty in the fatal shooting of Kate Steinle.
Lee served was a director of San Francisco's Human Rights Commission from 1991 to 1996 and served Newsom as the City Administrator from 2005 to 2011. He grew up in public housing in Seattle and worked early in his career as a civil rights attorney often representing low-income tenants.
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