The Federal Bureau of Investigation (FBI) used bitcoin wallet activity and an old exchange account as key evidence to arrest a Russian rapper on charges of conspiracy to commit money laundering.

In an affidavit unsealed earlier this week, FBI special agent Samantha Shelnick said she and her team had used the digital paper trail to uncover a major money-laundering operation, run by a shadowy criminal organization known as QQAAZZ. The rapper, Maksim Boiko, is believed to be closely connected to the leaders of the gang.

QQAAZZ received and laundered money for cybercriminals by changing fiat currency into crypto. The group had signed up for multiple exchanges, including Coinbase and Bitstamp, with the username “Atrofi95.” As these exchanges have KYC (know your customer) checks, FBI officials linked the accounts back to an email account controlled by an Aleksejs Trofimovics who, as the affidavit claims, regularly communicated with phone numbers associated with Boiko.

Boiko’s phones, used to communicate with Trofimovics, included multiple screenshots of bitcoin wallet addresses and transactions of up to $35,000. On further investigation, many of these pictures were found in conversations between Boiko and other suspected QQAAZZ members.

See also: The FBI Is Now Reaching Out to QuadrigaCX Victims

Suspicions were first raised for officials after Boiko and his wife tried to enter the U.S. with getting on for $20,000 in cash in January of this year. There were also multiple pictures on his phone, stretching back to 2015, showing him posing with large bundles of money. At the time, Boiko said the money came from revenue collected from rental properties in Russia, as well as investments he had made in bitcoin.

Per the FBI complaint, filed in the Western District of Pennsylvania, Shelnick said the agency also found multiple conversations between suspected cybercriminals and someone by the name of “gangass.”

They linked this pseudonym to Boiko via an account on BTC-e, a crypto exchange shut down in 2017 on suspicion that it was used to facilitate money laundering. Boiko had registered with an email containing his rap name, “Plinofficial,” and the moniker “gangass” as the username.

Boiko, who now stands accused of conspiracy to commit money laundering, has continued to release music under the label Smells Weed Music. He was still active on Twitter earlier this week. On Monday he said: “In Miami, zombie land is real. Everything is closed altogether.”

If found guilty, he faces up to 10 years imprisonment.