Schaefer's exit from the company was not unexpected, given the public issues between Schaefer and De La Hoya over the past few months, but the timing was a bit surprising -- a few days before De La Hoya's induction on Sunday into the International Boxing Hall of Fame.
"After more than 10 years with Golden Boy, it is time to move on to the next chapter of my career," Schaefer said in a statement. "This decision has required a great deal of personal reflection, but ultimately I concluded that I have no choice but to leave. I have succeeded in banking and I have succeeded in boxing, and I look forward to the next opportunity.
"I am proud to remain a shareholder, so I have a strong interest in the continued success of the company. I am proud of what we have accomplished at Golden Boy, but I now look forward to new challenges."
With no background in boxing, Schaefer, who handled Golden Boy's day-to-day business -- De La Hoya has been mostly a figurehead but recently vowed to take a more active role in the company -- built Golden Boy into the most significant promoter in boxing.
Under Schaefer's guidance, Golden Boy became a powerhouse. Schaefer was the point person in multiple record-breaking promotions, developed close relationships with HBO and later Showtime, closed an output deal for a boxing television series on Fox Sports 1, worked with numerous mainstream sponsors and made a deal to serve as the exclusive promoter of fights at the Barclays Center in Brooklyn, New York, while also maintaining a close relationship with the MGM Grand in Las Vegas.
Schaefer was also the one person at Golden Boy with a close, personal friendship with pound-for-pound and pay-per-view king Floyd Mayweather Jr., who used Golden Boy to promote all of his fights since 2007. Schaefer is also close to Mayweather's powerful adviser Al Haymon, whose A-client list is vast.
Schaefer has promoted the two biggest-selling pay-per-view events in boxing history, the 2007 showdown between Mayweather and De La Hoya, which generated a record of nearly 2.5 million buys, and the 2013 fight between Mayweather and Canelo Alvarez, which set the all-time pay-per-view revenue record ($150 million), all-time gate record ($20 million) and sold the second-most units (2.2 million).
Mayweather has said repeatedly he would not have worked with Golden Boy had it not been for Schaefer's presence.
Although Schaefer did not want to discuss the specific reasons for his departure, it has been no secret that while Golden Boy features many of Haymon's fighters on its cards, most of those fighters are not under promotional contract to the company, which became an issue between Schaefer and De La Hoya, who has virtually no relationship with Haymon.
Another issue between Schaefer and De La Hoya was Schaefer's refusal to do business with rival promoter Bob Arum of Top Rank. De La Hoya, who was promoted by Arum for most of his career, recently made up with him and has talked about their desire to work together again, which Schaefer was against.
Schaefer, who served as De La Hoya's business manager before they founded Golden Boy, said he tendered his resignation to De La Hoya in their Los Angeles office on Monday but did not want to go into details "or make too many further comments on the advice of my attorneys, but I am no longer working for Golden Boy. But I'm not going to discuss what Oscar and me discussed," he told ESPN.com. "Now I just have to see what I'm going to do next.
"When the time comes I will communicate what I am going to do. I wish it didn't end like this. I spent a lot of time with this company and I'm very proud of what I have accomplished. There's nothing to be ashamed about.
"When I left the banking business to go with Oscar I was the No. 1 private banker in the U.S. and I left happy. I moved on to a new challenge. I'm ready for another new challenge."
Speculation has been rampant that Schaefer would join Mayweather Promotions or found his own promotional company and work with Haymon's deep stable of fighters. While Schaefer declined to comment on that specific scenario, he did say that he likely would remain in the boxing promotion business.
"What I will do is reflect on all of this, but I believe one way or the other I will be involved in boxing," Schaefer said. "But I'm not going to talk about what I'm going to do or when I'm going to do it. It's a big day for me to walk away. I left on my own. I don't want to talk about it but, obviously, there were issues."
De La Hoya was not available for comment. He is being inducted into the Hall of Fame on Sunday and Schaefer will not attend.
On May 3, during the undercard of Mayweather's welterweight unification fight with Marcos Maidana, De La Hoya held a news conference in the MGM Grand media center, during which he addressed the problems with Schaefer but said he would not fire him and that he wanted him to stay at the company.
During the week of the fight, however, Schaefer said he and De La Hoya had not had a "meaningful" conversation in about a month. And even though both have been in the office regularly for the past few weeks, he said they did not talk.
Monday's resignation apparently caught De La Hoya by surprise. Just a couple of hours beforehand, De La Hoya did an interview with ESPN.com about his Hall of Fame career and was asked about Schaefer's future with the company.
"Things are getting worked out, our lawyers are talking," said De La Hoya, Golden Boy's majority shareholder. "My orders to my lawyer have been I don't want Richard to leave. I want him to stay. I don't know what Richard's lawyers have been talking to my lawyers about.
"Richard has been the CEO for many years and I don't want him to go. But Golden Boy is my baby and I'm going to do what's best for my company."