Bill Gross has left PIMCO for Janus Capital, Bloomberg reports. He'll be taking over the firm's global macro bond trading from Newport Beach, California. This is effective Monday.

CNBC's David Faber reports that Gross quit to preempt his own firing. For months he had been exhibiting erratic behavior. Employees at the firm threatened to abandon ship unless he left the trillion-dollar bond fund.

Bill Gross was the founder and chief investment officer of PIMCO. He is such a legend on Wall Street that he is known simply as "The Bond King." At PIMCO he made a $200 million salary.

“Bill Gross has an exemplary track record with decades of success and he will offer an exceptional approach to navigating today’s increasingly risky markets with a focus on macro, unconstrained strategies. His involvement provides Janus a unique opportunity to offer strategies and products that are highly complementary to those already managed by our credit-based fixed income team,” said Richard M. Weil, the chief executive of Janus Capital Group.

The problem is that things have changed in recent years.

Gross has had what MarketWatch called his "terrible, horrible, no good, very bad year" and was plagued by massive outflows for years — especially in the flagship fund he personally managed. As of August his PIMCO Total return fund had seen 16 straight months of outflows totaling $68 billion, cumulatively.

Matters were made worse when his respected co-CIO Mohamed El-Erian left the firm in January.

A public spiral followed shortly thereafter. Stories started flowing out of the powerhouse bond firm about Gross' management style. Employees described him as a showboat, and an aggressive one. His behavior became erratic at public conferences.

In June when he appeared on stage at the Morningstar annual investor conference to "Smooth" by Carlos Santana and Rob Thomas while wearing a pair of shades, people started to wonder — is something weird going on with Bill Gross? Watch the video below.

In recent weeks, Reuters reported that Gross had threatened to quit the firm.

And then finally this week, the news broke that regulators were investigating Gross' flagship Total Return ETF. They are trying to decide whether PIMCO undervalued assets within the security to make returns appear larger.

In a statement Gross said that Janus was "the right fit" for him because he would not have to deal with the "complexities" of managing a massive organization.

PIMCO doesn't seem that upset about the split either.

In a press release PIMCO said: “While we are grateful for everything Bill contributed to building our firm and delivering value to PIMCO’s clients, over the course of this year it became increasingly clear that the firm’s leadership and Bill have fundamental differences about how to take PIMCO forward.”

Here's the full press release from PIMCO:

September 26, 2014, (Newport Beach, CA): PIMCO, a leading global investment management firm, announced that Co-founder and Chief Investment Officer (“CIO”) William H. Gross, has resigned and will leave the firm, effective immediately. The firm has a succession plan in place and its Management Board, comprised of its Managing Directors, will confirm shortly the election of a new Chief Investment Officer. Relevant portfolio management assignments will also be announced at that time.

Said Mr. Hodge: “While we are grateful for everything Bill contributed to building our firm and delivering value to PIMCO’s clients, over the course of this year it became increasingly clear that the firm’s leadership and Bill have fundamental differences about how to take PIMCO forward.”

Mr. Hodge continued: “As part of our responsibilities to our clients, employees and parent, PIMCO has been developing a succession plan for some time to ensure that the firm is well prepared to manage a seamless leadership transition in its Portfolio Management team. Earlier this year, the firm established a new portfolio management leadership structure that reflects our long-held belief that the best approach for PIMCO’s clients and our firm is to evolve our investment leadership structure to a team of seasoned, highly skilled investors overseeing all areas of PIMCO’s investment activities.”

Said Michael Diekmann, Chief Executive Officer of Allianz Group: “Since becoming part of the Allianz Group in 2000, PIMCO has grown enormously and contributed consistently to Allianz’s success. We join our PIMCO colleagues in recognizing Bill Gross for his work over the 43 years since PIMCO’s founding. The management and investment structure put in place in January as well as the thorough succession planning gives us complete confidence in PIMCO’s investment and executive leadership team.”

Mr. Hodge added: “We have built a deep bench of talent with extensive investment and leadership experience, including more than 240 portfolio managers globally, and our outstanding team around the world gives us the scale, talent, expertise and commitment to manage this transition. We will continue to add and promote talent at all levels to help us drive our firm forward. We are energized and fully focused on serving our clients today and into the future.”

And check out the press release from Janus below:

William H. Gross Joins Janus Capital