(CNN) A California man pleaded guilty to identity fraud in a second case unsealed Friday by special counsel Robert Mueller in his investigation into Russian interference in the US presidential election.

The guilty plea results in the first criminal conviction related to Mueller's investigation into the Russian-backed ring of social media users aiming to interfere with the 2016 presidential election, prosecutors told a federal judge this month, according to unsealed court filing.

Richard Pinedo's guilty plea was unsealed by the federal court in DC on Friday, minutes after the Justice Department announced charges against 13 Russian nationals.

Pinedo's attorney said Friday his client was not aware of the identity or motivations of those buying the accounts.

Pinedo ran a scheme that helped his customers use dummy bank accounts to bypass the security of online companies like PayPal, which can be used to transfer money and pay for online services.

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