He rose through the ranks during a 30-year career at Kaiser to become CEO in 2013. During his tenure, the integrated health-care system and insurance giant grew from 9 million members, with more than 174,000 employees, to serve more than 12 million members with a workforce of 218,000. Under his leadership, the nation's largest nonprofit health system became a leading advocate in the movement to improve the delivery on care and benefits.
His sudden passing elicited an outpouring of tributes.
"Bernie was a good friend and trusted peer, and I am so saddened by his passing," said Larry Merlo, CVS Health CEO. "I'll miss Bernie's keen mind and good nature, as well as his unique ability to rally people from all walks of life around a singular goal of making health care better for all Americans."
"Bernard was a visionary leader with a passion for health equity, quality care and serving those in need," said Ceci Connolly, president and CEO of the Alliance of Community Health Plans. "His loss is a loss for all who strive to improve the quality of care and coverage in the American health care system."
"He truly 'walked the talk' in his concern for making health care not just a right, but something that is affordable and centered on the great diversity of patients," said Peter Lee, executive director of Covered California, the agency that runs the Affordable Care Act exchange in the Golden State.
Tyson's most recent push has been in the area of social determinants of health, economic and social issues in lower- income communities. Last spring, Kaiser launched a $200 million fund to help address some of those issues in the San Francisco Bay Area, half of which would address affordable housing and homelessness.
"We're here every day and making sure that we provide coverage. We have all kinds of financial assistance program for our members … so our incentives are all aligned to the community benefits and the well-being of the entire community," Tyson said on CNBC's "Closing Bell" last week, following an appearance at the network's At Work Summit in San Francisco.
Salesforce CEO Marc Benioff called Tyson an inspirational leader, tweeting Sunday, "A light in this world has gone out. … I will always remember him with love in my heart."
Kaiser Permanente did not disclose the cause of Tyson's sudden death. On Saturday, the executive had appeared at an Afro Tech event in Oakland, tweeting pictures of the gathering.
Tyson is survived by his wife, Denise Bradley-Tyson, and three sons.
Kaiser Permanente's board named Gregory Adams, executive vice president and group president, as interim chairman and CEO.
"The board has full confidence in Greg Adams' ability to lead Kaiser Permanente through this unexpected transition," Edward Pei, Kaiser board chairman of the executive committee, said in a statement.
Watch: Bernard Tyson on managing a multibillion dollar digital transformation