A federal judge on Monday sentenced a former Secret Service agent to nearly six years in prison following his conviction on charges related to the theft of electronic currency during a high-profile investigation into the online drug bazaar Silk Road.

Shaun Bridges' attorneys had sought a three-year prison term, but U.S. District Judge Richard Seeborg said Bridges' behavior was a "shocking and reprehensible abandonment of his public duty."

"This to me is an extremely serious crime consisting of the betrayal of public trust by a federal law enforcement agent," Seeborg said before issuing the 71-month prison sentence. "And from everything I see, it was motivated entirely by greed."

Bridges, who prosecutors said had previously spent time protecting the president's family, pleaded guilty in August to money laundering and obstruction charges and acknowledged stealing $820,000 worth of bitcoin after getting access to Silk Road, the multimillion-dollar marketplace for illegal drugs and other contraband. Bridges was part of a task force investigating Silk Road.

Prosecutors said in court Monday that Bridges then tried to pin the theft on a witness who was cooperating with the investigation, prompting Silk Road founder Ross Ulbricht to take out hits on the witness' life. Seeborg said it was "inexcusable" for a federal agent to put a cooperating witness at risk in that way.

Related: Corrupt Silk Road DEA Agent Carl Force Gets Over 6 Years in Prison

A tearful Bridges told the judge before his sentencing that he had accepted responsibility for his crime and had not spent any of the money he took. "I obviously have lost a lot, a very illustrious career," he said.

Ulbricht was sentenced in May to life in prison after he was convicted of charges accusing him of operating the website for nearly three years from 2011 until his 2013 arrest. Prosecutors say he collected $18 million in bitcoins through commissions on tens of thousands of drug sales while operating the site using the alias, "Dread Pirate Roberts."

A Drug Enforcement Administration agent on the Silk Road task force, Carl Force, was charged separately with selling information about the investigation and pleaded guilty to extortion and other charges. He was sentenced to 6½ years in prison in October.