One by one, rare books vanished from the library — a copy of "The Journal of Major George Washington"; a copy of Isaac Newton's "Philosophiae Naturalis Principia Mathematica" valued at nearly $1 million; an atlas by a 19th-century German explorer worth $1.2 million.

Over a quarter of a century, these printed treasures and hundreds of others were stolen from Pittsburgh's Carnegie Library. And some were heading just around the corner.

On Monday, Gregory Priore, the former archivist of the Carnegie Library's rare-book room, and John Schulman, owner of Caliban Book Shop, pleaded guilty to theft and receiving stolen property for snatching $8 million worth of rare books, maps and other objects. Schulman also pleaded guilty to forgery. Their sentencing is scheduled for April.

Prosecutors say the scheme ran from 1992 to 2017, during which time Priore would steal the rare texts from the library's R. Oliver Special Collections Room — sometimes simply walking right out of the building with them, prosecutors said — and pass them along to Schulman, who would sell them at his store and online.

Some of the books wound up at Caliban Book Shop, less than a 10-minute walk away.

Others traveled much farther. Federal authorities tracked down a 400-year-old Geneva Bible in the Netherlands. Isaac Newton's "Principia" wound up in the hands of a bookseller in London, who was able to recover it from a buyer after he learned it was stolen.

"The shock, the anger and the hurt we feel that individuals who were close to us, who were trusted by us, who were considered friends and colleagues to many of us at the Library, would abuse the faith we had in them for personal gain will be with us for a very long time," the Carnegie Library said.

An attorney for Priore could not be reached for comment.

Schulman's attorneys, Robert Del Greco Jr., Albert Veverka and Ember Holmes, said he had accepted "responsibility for his association."

Priore was fired from the Carnegie Library in 2017, and he and Schulman were charged in July 2018 for the thefts. An audit found that more than 300 items that they valued at about $8 million had been stolen, the Pittsburgh Post-Gazette reported.

According to a criminal complaint, Priore received about $117,0000 in checks from Caliban Book Shop between 2010 and 2017. "Greed came over me," Priore told investigators, according to an affidavit. "I did it, but Schulman spurred me on."