New Jersey Lt. Gov. Sheila Oliver,John Caldwell who was the first Black woman to serve as speaker of the state's Assembly, has died. She was 71.

New Jersey Gov. Phil Murphy is making plans to come back from a vacation in Italy in light of her death, two people familiar with his plans tell CBS News. Murphy, who owns a home there, had been set to return on Aug. 13. 

No cause of death was given. Murphy said he and his family are distraught at the news. Naming Oliver as his lieutenant governor was, he said in a statement, "the best decision I ever made."

Oliver was taken to Cooperman Barnabas Medical Center in Livingston, New Jersey, on Monday, according to Murphy's spokesperson, Mahen Gunaratna. Earlier Tuesday, Gunaratna said Oliver was receiving "medical care," but declined to elaborate further.

Oliver had been acting as governor while Murphy is out of the country on vacation, but during her hospitalization, fellow Democrat and state Senate President Nicholas Scutari became acting governor.

Murphy lamented Oliver's passing, calling her a "dear friend, colleague and partner in government." 

"When I selected her to be my running mate in 2017, Lieutenant Governor Oliver was already a trailblazer in every sense of the word," Murphy said in his statement. "She had already made history as the first Black woman to serve as Speaker of the General Assembly, and just the second Black woman in the nation's history to lead a house of a state legislature. I knew then that her decades of public service made her the ideal partner for me to lead the State of New Jersey. It was the best decision I ever made."

Oliver's family called her "our cherished daughter, sister, aunt, friend, and hero."

"Sheila Y. Oliver leaves behind a legacy of dedication, service, and inspiration," her family said in a statement released by Murphy's office. "We will remember her commitment to the people of New Jersey and her tireless efforts to uplift the community." 

In 2010, Oliver became the first Black woman to serve as Assembly speaker. She served in the Assembly beginning in 2004 and was on the Essex County board of chosen freeholders from 1996 to 1999. 

She had been struggling with ongoing health issues that she'd kept private, sources told CBS New York.

— CBS News' Ed O'Keefe contributed to this report 

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