A volunteer at one of the world’s largest privately held Holocaust archives was arrested here Wednesday, accused of pilfering thousands of priceless documents to sell online.Authorities said Mansal Denton, 20, began volunteering at The Mazal Holocaust Library in Hill Country Village in June 2009, assigned to scan documents to put on the non-profit’s website. He continued to make sporadic appearances at the facility up until last week, court documents state.After his North Side home was searched Wednesday by district attorney’s office investigators, the Texas Rangers and Hill Country Village police, Denton was charged with second-degree felony theft between $100,000 and $200,000.But the investigation is ongoing and that rough estimate of the property value could rise, said Adriana Biggs, chief of the district attorney’s white collar crimes division. Investigators decided to make an arrest immediately because Denton was scheduled to take a trip to Poland on Thursday, she said.“The theft at issue is not a theft of money or property that can be replaced. This is a theft of history,” district attorney’s office investigator Jesse De Los Santos wrote in an affidavit requesting the search warrant. “These documents appear to be unique, original, authentic and priceless.