SACRAMENTO — A Vallejo man who appears to have accidentally led authorities to a large-scale heroin ring run by incarcerated members of the Aryan Brotherhood will receive leniency for pleading guilty to drug trafficking charges, court records show.

Brian C. Butler, 60, pleaded guilty to a charge of conspiracy to distribute at least 100 grams of heroin, a federal offense, in an April 26 hearing before Chief District Judge Kimberly J. Mueller, court records show. In exchange, federal prosecutors agreed to seek a “low-end guidelines sentence” against Butler, who faces a minimum of five years in prison.

The plea agreement with Butler required him to sign a document acknowledging he sold a total of 368 grams of heroin — or 0.8 pounds — to an undercover agent over eight months, drugs he was reportedly receiving from his co-defendant, Vincente Castro Zavaleta. Butler admitted that on Feb. 17, 2016, he drove to a Jack in the Box in Concord to pick up drugs from Zavaleta, then met the undercover agent in the power tool aisle of the Home Depot in Vallejo, where he gave the agent a quarter-pound of heroin in exchange for $2,950.

Butler was investigated by the Drug Enforcement Administration in June 2015, when he started selling heroin to the agent, according to the plea agreement. During the eight-month investigation that followed, authorities not only identified Butler’s suspected supplier but developed leads that led to wiretaps of people connected to the Aryan Brotherhood prison gang, including its alleged leaders.

In court records filed in 2019, prosecutors said the investigation into Butler led investigators to an alleged Sacramento heroin ring run by Jeanna Quesenberry, who also allegedly sold heroin to an undercover agent. At the time, authorities say Quesenberry was in regular contact with Ronald Dean Yandell, 58, an alleged leader of the Aryan Brotherhood who was serving a life sentence in Sacramento.

The DEA eventually wiretapped contraband prison cell phones obtained by several alleged Aryan Brotherhood members, including Yandell. The result was four 2019 indictments charging two dozen alleged Aryan Brotherhood members and associates with crimes ranging from drug trafficking to murders and murder conspiracies. These included Arturo Castro Zavaleta, an alleged Turlock-area heroin dealer who authorities say was attempting to grow his own opium and supplied Vincente Zavaleta.

Aside from Butler, only one other person — an alleged drug courier and Aryan Brotherhood associate named Samuel Keeton — has agreed to plead guilty. Everyone else continues to fight the case, which appears no closer to going to trial than it did when it was filed two years ago.

In a second round of charges tied to the Aryan Brotherhood investigation, last November state and federal prosecutors charged more than 100 people — including incarcerated members of the prison gang and others connected to a white gang known as the Fresnecks — with drug and gun trafficking in the Central Valley. Some of the defendants were reportedly supplying meth and heroin to large-scale dealers in Montana.

In pleading guilty, Butler avoids a potential maximum 40-year prison term. His sentencing has been tentatively set for July 12, and he remains at the Sacramento jail in the meantime.

Butler’s prosecution has been mostly kept out of the public’s eye. More than 30 documents in the case have been filed under seal, with the exception of the plea agreement, the indictment, and several insignificant filings to re-schedule court hearings. Similarly, prosecutors did not issue a news release after Butler pleaded guilty.

Butler, like many others charged in the DEA investigation, appears to have been able to obtain cellphones while he was incarcerated. On his Facebook page in September 2019 was an undated, shirtless photo of Butler, his arms outstretched, standing inside of a prison cell. On his chest were tattoos of a swastika and an “SS” in lightning bolts font, two symbols commonly associated with white supremacist prison gangs. The day after a story appeared in this newspaper reporting the federal case against Butler, the picture was no longer publicly viewable.