Billionaire hedge fund founder turned environmental warrior Tom Steyer, a leading Democratic candidate for California governor, is facing mounting questions about how he earned his wealth - notably investments in private prisons that are now being used to house undocumented immigrants facing deportation.

Some of the most vicious political attacks come from his Democratic rivals and Sacramento special interest groups as the June 2 primary election fast approaches, but Steyer has been dogged for years about his past, controversial business ventures and how they help fund his unbridled campaign spending.

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Steyer, 68, faced that ire during a town hall event in San Diego last week.

"Tom, you're not going to come to San Diego and ignore this detention center," Holly Taylor, a 37-year-old Democrat screamed at Steyer, holding signs with QR codes to help detainees at an Otay Mesa private prison that Steyer's hedge fund backed. "It's a concentration camp. They're drinking water out of a toilet."

Taylor, a crime scene cleaner from Pacific Beach, is among scores of people who gather weekly at the facility to raise money for detained immigrants to provide them some comfort amid the Trump administration's Immigration and Customs Enforcement raids.

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In 1986, Steyer, co-founded Farallon Capital, which had shares valued at $89.1 million in the Corrections Corp. of America in 2005, according to the Securities and Exchange Commission. That company, now known as CoreCivic, operates private prisons around the nation that are housing people picked up by federal immigration agents, including the one in Otay Mesa.

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It is not the first time Steyer has faced criticism about the connection with private detention facilities. At the California Democratic Party convention in February, protesters dressed in orange prison jumpsuits sought to draw attention to the controversy.

His Democratic rivals have also seized upon the issue to question the billionaire's progressive credentials.

"Before he was a progressive, he made millions off of companies that operate ICE detention centers, that operate private prisons that incarcerated young children," state Superintendent of Public Instruction Tony........

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