The series of $500,000 payments Ippei Mizuhara sent from Shohei Ohtani's bank account to an illegal bookmaking operation were forwarded to California and Las Vegas casinos, where the money was deposited in gambling accounts, converted to playing chips and later cashed out to pay the bookie, multiple sources with direct knowledge of the operation told ESPN.

The description of what happened to Ohtani's money sheds new light on the ongoing federal probe that drew global attention after his interpreter, Mizuhara, was accused of stealing $16 million from the Los Angeles Dodgers slugger to feed what he has called a gambling addiction.

Mathew Bowyer, the California bookmaker who took Mizuhara's bets, was a frequent customer at Las Vegas casino Resorts World. The sources told ESPN that Mizuhara paid his losses to Bowyer's associate, who forwarded the money to his own "marker" accounts at Resorts World and Pechanga Resort Casino in Southern California. The men then withdrew chips from the marker account, gambled with them, and if they won, cashed out.

Bowyer, 49, lost $7.9 million at Resorts World from June 2022 to October 2023, according to multiple sources. After Bowyer's home was raided by federal agents on Oct. 5, he was dubbed a known bookmaker and banned from entering casinos throughout the United States, according to sources with direct knowledge of the ban.

Neither Bowyer nor his associate has been named in any indictment unsealed to date.

Attorneys for both Bowyer and his associate declined to comment.

Multiple sources told ESPN that Resorts World is at the center of what federal authorities described in an affidavit as an investigation into "illegal sports bookmaking organizations operating in Southern California, and the laundering of the proceeds of these operations through casinos in Las Vegas." Twelve people have been charged or convicted to date, and two Vegas casinos have agreed to pay fines, according to the affidavit. Resorts World was served a federal subpoena last August that sought, among other things, documents related to its anti-money laundering policies.

A spokesperson for Resorts World told ESPN the casino does not comment on ongoing legal matters. "Resorts World Las Vegas takes any suggestion of violations seriously and is cooperating with the ongoing investigation," the spokesperson said.

Resorts World opened its doors to the public in 2021 under the leadership of Scott Sibella, who was MGM Grand's president from 2011 until he left for Resorts World in 2019. Sibella pleaded guilty to charges that, as president of MGM Grand, he failed to file suspicious activity reports about another Southern California bookie, Wayne Nix.

Nix, a former minor league baseball player, awaits sentencing after pleading guilty to operating an illegal gambling business and filing a false tax return. His clients included NBA legend Scottie Pippen, former MLB All-Star Yasiel Puig and Maverick Carter, the longtime friend and business manager of NBA superstar LeBron James.

The Nevada Current reported that Resorts World received a federal grand jury subpoena in August seeking "documents relating to the Company's Anti-Money Laundering policies, Know Your Customer practices, policies and practices relating to extensions of credit, comps or other benefits, use of promotional chips, and other customer transactions."

In September, Resorts World fired Sibella for "violating company policies."

On Oct. 5, federal agents raided Bowyer's home, seizing computers, cell phones, jewelry, luxury handbags, a money counting machine, cash and chips from several casinos, according to search warrant documents obtained by ESPN.

Federal agents, according to the documents, were authorized to seize records that could show evidence of Bowyer committing federal crimes, including transmission of wagering information, operation of an illegal gambling business, structuring to evade reporting requirements, and laundering the proceeds of an illegal gambling business.

Multiple sources told ESPN that Bowyer, who has worked as a commodity broker and owns a Brazilian jiu-jitsu studio, got into the bookmaking business more than 20 years ago. It became his primary source of income soon after the 2008 financial crisis, when he befriended bookmaker Owen Hanson, the former USC football player convicted of running an international drug trafficking, gambling and money laundering operation. Hanson went to federal prison on a 21-year sentence in 2017 but had his sentence reduced and was released in March.

Unlike sportsbooks, where customers have to front money, bookies allow people to bet on credit. Mizuhara, who was one of more than 600 bettors with Bowyer's book, ran up a debt of $40.7 million, according to federal authorities.

In an interview about the Mizuhara investigation, which included several text exchanges between the interpreter and Bowyer, Tyler Hatcher, the special agent in charge at IRS Criminal Investigation in Los Angeles, told ESPN that Bowyer's behavior was "typical of bookies."

"They're salesmen, right?" he said. "Their job is to ... try to get them to continue to play. That's what I saw. Just another salesman continuing to say, 'Oh, it's OK.' You know, 'we'll get it next time.'"

Hatcher would not discuss the investigation into Bowyer.

Bookmakers like Bowyer typically rely on agents, or sub-bookies, to find clients. According to a bookmaker who spoke on condition of anonymity, the agents are paid returns of anywhere from 10% to 50% of a losing bet, depending on the value of the client.

"It depends on the arrangement. I've had it where I give 10% regardless if they win or lose because I want the customer and he's going to lose in the long run," the bookmaker said.

In a state where sports betting is not legal, Bowyer is among a small group of bookmakers who compete with each other for business but also work together, running credit checks on potential customers and flagging "sharps," or professional gamblers, according to sources with firsthand knowledge of bookmaking operations.

"We cross-reference clients. We call each other," the bookmaker said. "It's a very small network of guys. There are only 10 big names in the business. Everyone else is an agent."

Sources familiar with Bowyer's operation told ESPN that Bowyer has a long history with casinos, which he uses for both business and pleasure.

Bowyer is known in Vegas as a "whale," a high-stakes gambler unafraid to lose millions on the casino floor. He has a reputation of bringing anywhere between $250,000 to $1 million each visit, which was as often as two or three times a month, the sources said.

He often brought a small group of friends who, according to the sources, coordinated bets and consolidated their balances at the end of their trip.

Casino employees are required to file suspicious activity reports for red flag behavior or when they know or suspect that money for any transaction over $5,000 is derived from illegal activity.

Resorts World did not answer ESPN's questions about whether Bowyer's activities triggered any such reports.

Failure to file these reports is a federal crime, to which Sibella pleaded guilty as part of the Nix investigation. Sibella could face a maximum sentence of five years in prison and a $250,000 fine. His sentencing is scheduled for May 8 in Los Angeles.

According to multiple sources with direct knowledge, Bowyer; his wife, Nicole; and their small circle of associates began making regular trips to Resorts World after it opened in 2021. Bowyer dropped more than $800,000 in his first visit, the sources said.

In return, Bowyer and his group received high-end "comps" through his casino host, who earned money in commission based on how much they gambled. The comps included free food and beverage, golf, tickets to shows and sporting events, shopping sprees, hotel suites and promo chips.

Resorts World, where Sibella was then president, authorized Nicole Bowyer to replace Bowyer's casino host, allowing the couple to recoup some of his losses through payments to his wife, the sources told ESPN.

Even before the current federal investigation into his bookmaking activities, Bowyer had been "86'd," or banned, from Vegas casinos like MGM Grand, the Palazzo and the Venetian, according to the sources. The Palazzo and the Venetian later reinstated him.

Records from his 2011 bankruptcy filing show Bowyer declared $425,000 in gambling losses at the Cosmopolitan and Aria casinos in Las Vegas between 2010 and 2011.

In 2015, Bowyer received a $1.2 million line of credit from the Foxwoods Resort Casino in Connecticut, which sued him three years later in tribal court to get the money back, according to court filings. As of last year, the Mashantucket Pequot Tribal Nation that owns the casino was still trying to recoup its funds.

ESPN's Paula Lavigne and John Mastroberardino contributed to this report.