Swiss prosecutors froze more than $1 billion held in bank accounts belonging to Bob Brockman, who’s been charged in the U.S. for alleged tax evasion and money laundering. Reynolds and Reynolds Co. announced Friday that Brockman stepped down as CEO and chairman of the dealer management system giant.

A spokeswoman at the Geneva prosecutor’s office said that accounts were frozen but didn’t specify what banks held the funds.

Brockman was indicted in October by U.S. federal prosecutors for allegedly using a network of secret Caribbean entities to evade taxes on $2 billion in investment income in what may be the largest prosecution of its kind in U.S. history. Brockman is accused of using a Bermuda-based family charitable trust and other offshore entities to hide assets from the Internal Revenue Service while failing to pay taxes. He was also charged with money laundering and other crimes.

The case is “the largest-ever tax charge against an individual in the United States,” David Anderson, the U.S. prosecutor in San Francisco, said last month.

A message left with Brockman’s lawyer asking about his Swiss bank accounts wasn’t immediately returned. The U.S. Department of Justice didn’t immediately reply to a request for comment.

About $950 million is held at Mirabaud & Cie., according to local blog Gotham City, which first reported on the asset freeze.

According to his Oct. 1 indictment, Brockman instructed someone identified as “Individual One” to open an account for him at Geneva-based Mirabaud in 2010. There are further references in the 42-page document to transfers in and out of three Mirabaud accounts Brockman allegedly controlled.

A spokesman for Mirabaud declined to comment.

Prosecutors were helped by Robert Smith, the CEO of Vista Equity Partners, who set up his private equity fund 20 years ago with a $1 billion injection from Brockman’s trust. Smith avoided prosecution by agreeing to cooperate against Brockman. He also admitted he failed to pay $30 million in taxes, and will pay $140 million in back taxes, fines, and penalties, according to people familiar with the matter.

Brockman faces a 39-count indictment returned by a San Francisco grand jury and unsealed on Oct.15. Appearing by video conference from Houston the same day, Brockman pleaded not-guilty to the charges and denied the government’s allegations that he should forfeit proceeds from wire fraud.

The court agreed to allow Brockman to post $1 million bond, remain out of custody and to travel to several parts of the U.S. to meet with his lawyers and conduct business.