SAN FRANCISCO — In a stunning criminal complaint, State Sen. Leland Yee has been charged with conspiring to traffic in firearms and public corruption as part of a major FBI operation spanning the Bay Area, casting yet another cloud of corruption over the Democratic establishment in the Legislature and torpedoing Yee’s aspirations for statewide office.

Yee and an intermediary allegedly met repeatedly with an undercover FBI agent, soliciting campaign contributions in exchange for setting up a deal with international arms dealers.

At their first face-to-face meeting in January, “Senator Yee explained he has known the arms dealer for a number of years and has developed a close relationship with him,” an FBI affidavit says, noting Yee told the agent the arms dealer “has things that you guys want.”

Yee, D-San Francisco, highlights a series of arrests Wednesday morning that included infamous Chinatown gangster Raymond “Shrimp Boy” Chow, whose past includes a variety of charges including racketeering and drug crimes. Targets of the early-morning raids appeared in federal court in San Francisco on Wednesday afternoon.

A 137-page criminal complaint charges 26 people — including Yee and Chow — with a panoply of crimes, including firearms trafficking, money laundering, murder-for-hire, drug distribution, trafficking in contraband cigarettes, and honest services fraud.

Yee is charged with conspiracy to traffic in firearms without a license and to illegally import firearms, as well as six counts of scheming to defraud citizens of honest services. Each corruption count is punishable by up to 20 years in federal prison and a fine of up to $250,000, while the gun-trafficking count is punishable by up to five years and $250,000.

The charges are particularly shocking given that Yee has been among the state Senate’s most outspoken advocates both of gun control and of good-government initiatives.

“It seems like nobody knew this was coming, and everyone is astounded by the allegations,” said Corey Cook, director of the University of San Francisco’s Leo T. McCarthy Center for Public Service and the Common Good. “I’m just astonished… Political corruption is one thing, but this is a whole other level.”

San Francisco political consultant Keith Jackson, a former school-board president, allegedly was the link between Yee and Chow, who federal prosecutors say is the current “Dragonhead,” or leader, of the San Francisco-based Ghee Kung Tong organization, spelled in court documents as Chee Kung Tong.

Chow introduced an undercover agent who had infiltrated his organization to Jackson, who with his son, Brandon Jackson, and another man, Marlon Sullivan, allegedly sold the agent various guns and bulletproof vests. The Jacksons and Sullivan also allegedly conspired in a murder-for-hire scheme requested by the undercover agent, as well as other crimes including sale of stolen credit cards and purchase of cocaine.

An FBI affidavit says Keith Jackson starting last August told one of the undercover agents that Yee was “associated with a person who was an international arms dealer who was shipping large stockpiles of weapons into a foreign country.” At later meetings in August and December, Jackson said Yee had agreed to help set up an arms deal; the agent first gave Jackson $1,000 cash for his help, and later cut a $5,000 check from a bogus company to Yee’s campaign.

Finally, Yee and Keith Jackson met Jan. 22 with the undercover agents at a San Francisco coffee shop, the affidavit says.

“According to Senator Yee, the arms dealer is ‘low-key’ and has been trafficking weapons for quite a while,” the document says. “According to Senator Yee, the arms dealer sourced the weapons from Russia.”

“Senator Yee said of the arms dealer, ‘He’s going to rely on me, because ultimately it’s going to be me,'” the affidavit says. “Senator Yee said, ‘I know what he could do. I have seen what he has done in the past on other products and this guy has the relationships.’ Senator Yee emphasized that the arms dealer took baby steps and was very careful.”

Yee told the agent that the arms dealer had contacts in Russia, Ukraine, Boston and Southern California, the affidavit says, and the agent asked Yee for a commitment. “Senator Yee said, ‘Do I think we can make some money? I think we can make some money. Do I think we can get the goods? I think we can get the goods.'”

The agent told Yee and Jackson he wanted any type of shoulder-fired weapons or missiles, the affidavit says; Yee asked whether he wanted automatic weapons, and the agent confirmed he did — about $500,000 to $2.5 million worth. Yee told the agent “he saw their relationship as tremendously beneficial,” the affidavit says, adding he wanted the agent and Jackson to make all the money because he didn’t want to go to jail. The agent replied he would pay Yee and Jackson hundreds of thousands of dollars over time, and more immediately would pay $100,000 for the first arms deal. “Senator Yee said ‘Alright, take care.’ The meeting ended.”

But by their next meeting on Feb. 25, Yee had grown spooked by the federal indictment of state Sen. Ronald Calderon; the two shared a desk on the Senate floor. “Senator Yee thought the other state Senator was a classic example of involving too many people in illegal activities,” the affidavit says. Pressured by the agent to arrange an arms deal, Yee encouraged the agent “to start off doing small deals with the arms dealer” with Yee as an intermediary.

“Senator Yee stated he was unhappy with his life and said, ‘There is a part of me that wants to be like you. You know how I’m going to be like you? Just be a free-agent out there,'” the affidavit says, adding Yee told the agent “he wanted to hide out in the Philippines.”

The agent met again with Yee on March 5, and Yee discussed a new potential arms dealer named Wilson Lim. The agent said his family in New Jersey wanted to support Yee’s bid for Secretary of State, to which Yee responded, “I can be of help to you for 10 months or I can be of help to you for eight years. I think eight years is a lot better than 10 months.”

Yee discussed specific locations in the Philippines and Florida that might be ideal for moving the guns, which he said would include M-16-type automatic rifles.

Yee, Jackson, Lim and the agent met again March 11; Yee said the arms deal wouldn’t be done until after this year’s elections. “Senator Yee explained, ‘Once things start to move, it’s going to attract attention. We just got to be extra-extra careful.'”

Finally, they all met March 14, where they discussed how they would break up the undercover agent’s money into legitimate campaign donations. The agent told Yee he was prepared to give Yee $6,800 cash and a list of weapons he wanted; Yee replied “he would take the cash and have one of his children write out a check.”

Yee ran for mayor of San Francisco in 2011 and now is a candidate for California Secretary of State. But the criminal complaint likely ruins his candidacy and further threatens Democrats’ efforts to restore their state Senate supermajority that already has been broken by two other lawmakers’ paid leaves of absence to deal with criminal charges.

Keith Jackson and Yee from 2011 until now allegedly solicited donations from undercover FBI agents in exchange for official acts and conspired to traffic firearms, the complaint says. Starting in May 2011, Jackson solicited an undercover FBI agent to give money to Yee’s mayoral campaign, including asking the agent for donations in excess of the $500 individual donation limit. The agent refused, but introduced Jackson and Yee to a purported business associate — another undercover agent — who they also solicited for at least $5,000.

Yee’s mayoral election loss left him with $70,000 in debt, the complaint says, and so Yee and Jackson allegedly agreed that Yee would call a California Department of Public Health manager in support of a contract under consideration with the second undercover agent’s purported client, and would provide an official letter of support for the client, in exchange for a $10,000 campaign donation. Yee allegedly made the call on Oct. 18, 2012, and provided the letter on or about Jan. 13, 2013; Jackson allegedly accepted the $10,000 cash donation on Nov. 19, 2012.

Yee had yet to appear before the judge as of 3 p.m., but earlier in the afternoon the judge ordered Chow be held without bail. Government attorneys called him a flight risk and danger to the community, citing his criminal history. Chow’s lawyer objected saying that Chow has been fighting with immigration authorities to stay in the United States.

Chow is not a U.S. citizen. He is being represented by public defender and lives in San Francisco with his girlfriend. He has been on electronic monitoring since he’s been out of prison and seeking legal immigration stays, even during the current investigation.

FBI agents and local police served arrest and search warrants throughout the Bay Area, with agents seen in San Francisco and San Mateo and Yee’s Capitol office in Sacramento. One of the searches was at the San Francisco Chinatown office of the Ghee Kung Tong Free Masons and is linked to Chow’s arrest.

Outside that building on Spofford Street — a Chinatown alley between Clay and Washington streets — FBI Special Agent Michael Gimbel would say only that “the FBI is executing numerous search warrants around the Bay Area.”

San Francisco firefighters carried a heavy rotary saw into the building late Wednesday morning; neighbors said they believe there’s a safe inside the building. Federal agents removed about 10 boxes of documents and several bags of material from the building at about 12:30 p.m., and the FBI left the scene soon after that.

Federal law enforcement officials have been chasing Raymond “Shrimp Boy” Chow for decades, branding him one of the longtime Bay Area leaders of a Hong Kong-based criminal syndicate called the Wo Hop To. Chow’s criminal rap sheet dates back to 1978, and includes federal racketeering indictments that have alleged attempted murder, murder-for-hire, gun trafficking and other crimes.

Chow was originally indicted in a federal racketeering probe that targeted the alleged leader of the Chinatown gang, Peter Chong. At one point, Chow cooperated with federal law enforcement officials against Chong, who had fled to Hong Kong after being indicted on racketeering charges but was later extradited and convicted in San Francisco federal court in a case marred by setbacks and delays. Chow’s original 1995 sentence of 24 years was cut to 11 years as a result of his cooperation, and he has been out of prison for 10 years.

During an afternoon press conference, State Senate President Pro Tem Darrell Steinberg, D-Sacramento, said “Leland Yee should leave the Senate and leave it now.”

Yee represents San Francisco and a portion of San Mateo County. Before becoming the first Chinese-American ever elected to the state Senate in 2006, Yee was an assemblyman from 2002 to 2006; a San Francisco supervisor from 1997 to 2002; and had been a member and president of the San Francisco Unified School District board. While in the Assembly, he was the first Asian-American to be named Speaker pro Tempore, essentially making him the chamber’s second-most-powerful Democrat.

That power would have been exercised this year in Yee’s run for Secretary of State against state Sen. Alex Padilla, D-Van Nuys; Democrat Derek Cressman; Republican Pete Peterson; and nonpartisan Dan Schnur.

Upon pulling his candidacy papers in February, Yee issued a news release saying it was time for a Secretary of State “who will expand access to the ballot box, make our government more transparent, and strengthen California’s democracy.”

“I am committed to empowering Californians so that they can guarantee fair elections, expose special interests and prevent corruption, because it’s your California,” Yee said at the time.

Yee campaign spokesman Joaquin Ross declined to comment Wednesday morning, saying he would have to call back.

Yee is the state’s third Democratic legislator recently targeted in corruption allegations. In February, State Sen. Ron Calderon, D-Montebello, surrendered to authorities after being indicted on bribery charges. In January, state Sen. Roderick Wright, D-Inglewood, was convicted of voter fraud and perjury stemming from a 2010 indictment.

Cressman, who until last June was vice president of the nonpartisan government watchdog group Common Cause, Wednesday morning said that charges against Yee must be “a wake-up call” given other Senate Democrats’ legal problems.

“We are clearly beyond the point of looking at one bad apple and instead looking at a corrupt institution in the California Senate,” Cressman said. “The constant begging for campaign cash clearly has a corrosive effect on a person’s soul and the only solution is to get big money out of our politics once and for all.”

Schnur, a longtime GOP campaign strategist who more recently served as chairman of the state Fair Political Practices Commission and directed the University of Southern California’s Unruh Institute of Politics, said news of Yee’s arrest “is yet another in a series of reminders of why Californians have so little trust in their elected officials.

“My hope is that this will prompt the Legislature to take much more aggressive and meaningful action to fix a broken political system than they have been willing to do to date,” Schnur said.

Yee emigrated to San Francisco from China at age 3; his father was a veteran who served in the Army and the merchant marine. Yee earned a bachelor’s degree from UC Berkeley; a master’s degree from San Francisco State University; and a doctorate in child psychology at the University of Hawaii. He and his wife, Maxine, have four children.

Rep. Jackie Speier, D-Hillsborough, served with Yee for several years in the Legislature but was never close to him. She said the senator is innocent until proven guilty but called the allegations “regrettable.”

“It’s always sad for all of us in the profession,” said Speier, “to see individuals who lose sight of what the public trust is all about.”

Check back later for updates to this story.

Staff writers Thomas Peele, Mark Gomez and Erin Ivie contributed to this report.