The move was an open plea to Judge Kathleen Kennedy and was not a settlement with prosecutors, the D.A.'s office said.
"Although we were prepared to go to trial and felt confident we could convict Mr. Rizzo of all charges, we are pleased he chose to admit his guilt and accept full responsibility for the irreparable harm he caused the people of Bell," said District Attorney Jackie Lacey in a statement.
An audit by the California State Controller's Office previously found that the city had illegally raised property taxes, business license fees and other sources of revenue to pay the salaries of Bell officials.
Rizzo was believed to be the ringleader of the corruption scheme. City records revealed that Rizzo had an annual salary and compensation package worth $1.5 million, making him one of the highest paid administrators in the country. Rizzo's salary alone was about $800,000 per year.
Sentencing for Rizzo is scheduled for March 12, 2014. Kennedy says she will sentence Rizzo to a minimum of 10 years and a maximum of 12 years in state prison, making the sentence the longest for anyone convicted of public corruption since the Public Integrity Division was established in 2000, the D.A.'s office said.
It's still not nearly enough time, according to some Bell residents.
"Mixed emotions today because it's an easy way out," said Marcos Oliva of Bell. "Six years, he'll probably be out and enjoying his millions. That's why people are very upset."
The surprise plea came less than a week before jury selection was to begin for his trial. His co-defendant, former assistant city manager Angela Spaccia, is still scheduled to go to trial Monday.
Rizzo's attorney James Spertus says his client will cooperate with the state's trial against Spaccia.
"His conduct sends a clear message that he's accepting responsibility for wrongdoing that happened during his tenure at the city of Bell," Spertus said.
According to Spertus, the no-contest plea will allow Rizzo to eventually serve the sentence from the state charges concurrently with the future sentence from pending federal charges against him.
The plea brings closure for some, but others at City Hall trying to rebuild the city's credibility say the process will take years.
"He left this city $100 million in debt," said Bell City Manager Doug Willmore.
The D.A.'s office says Rizzo will need to give the city of Bell $3.2 million. However, a final amount has not yet been determined.