The specific cause of O'Connor's death has not been released, but it appears that she had been sick in the days leading up to her passing. On January 26 Hefner tweeted that his wife, Crystal, was visiting O'Connor, who was "not doing very well."
Crystal is going to visit Mary O'Conner, who is not doing very well. Mary has our prayers. We all love her.
Hefner then announced late last night that O'Connor passed away:
Mary passed away today. We loved her more than words can say.
It's clear that O'Connor was well-loved by the many girls who passed through the doors of the Playboy mansion. Current and former playmates are tweeting their condolences and expressing their love for O'Connor:
Hef's long time secretary & my dear friend Mary O'Connor has passed away. It's a very sad day here at the Playboy Mansion. We love you Mary.
R.I.P. Mary O Connor from Playboy She was Hef's secretary for 50 years. She was our "den mom" and angel in the house. She will be missed.
RIP Mary O'Connor. She was an amazing person who helped me through so much. But I know she's happy with her boo Captain Bob.
In addition to her work for Playboy, O'Connor made multiple appearances on the reality show The Girls Next Door: