Tech executive David Goldberg, head of the online SurveyMonkey site and husband of Facebook executive Sheryl Sandberg, has died.
Mr Goldberg died suddenly last night, brother Robert Goldberg wrote on his Facebook page.
"Dave Goldberg was an amazing person and I am glad I got to know him," Facebook founder Mark Zuckerberg wrote on his own page.
"My thoughts and prayers are with Sheryl and her family."
Ms Sandberg is the author of Lean In: Women, Work And The Will to Lead.
The San Francisco Chronicle reports that Mr Goldberg, 47, was a former Yahoo executive and was credited by Ms Sandberg for helping her juggle her roles as an executive and mother.