Eccentric antivirus software company founder John McAfee was found dead in his prison cell in Barcelona, Spain, on Wednesday, shortly after Spain’s National Court approved his extradition to the United States to face criminal tax evasion charges.

The prison’s medical professionals attempted to resuscitate him. McAfee was being held at the Brians 2 prison in Catalunya.

McAfee was arrested last October at the international airport in Barcelona on the tax evasion charges, which are pending in federal court in Tennessee. He had been held in jail in Spain since then.

According to the indictment, McAfee earned millions of dollars in income from promoting cryptocurrencies, consulting work, speaking engagements, and selling the rights to his life story for a documentary.

“From 2014 to 2018, McAfee allegedly failed to file tax returns, despite receiving considerable income from these sources,” the U.S. Justice Department said in October.

McAfee also was charged in Tennessee federal court in March with failing to report income he made from promoting cryptocurrencies.

The Justice Department has said that McAfee and others involved in that so-called scalping scheme bought large amounts of cheap cryptocurrency altcoins, then aggressively promoted them online with “false and misleading endorsement tweets” to artificially inflate their market prices.

“McAfee Team members collectively earned more than $2 million in illicit profits from their altcoin scalping activities,” the Justice Department said earlier this year.

Last week, McAfee tweeted about his criminal case, writing, “The US believes I have hidden crypto. I wish I did but it has dissolved through the many hands of Team McAfee (your belief is not required), and my remaining assets are all seized.”

“My friends evaporated through fear of association. I have nothing. Yet, I regret nothing,” wrote McAfee in the tweet, which is pinned to the top of his Twitter feed.

The Securities and Exchange Commission in a civil lawsuit last October accused McAfee of making more than $23 million in undisclosed income from false and misleading cryptocurrency recommendations.

McAfee resigned from the eponymous antivirus software company he founded in 1994.

In 2013, he created a profane parody video explaining how users can uninstall the software.

In 2019, a federal court in Florida ordered McAfee to pay more than $25 million in damages to the estate of a Florida man named Gregory Faull, who allegedly was murdered in the nation of Belize at the direction of McAfee in 2012.

Faull owned a property along a beach next to McAfee, two of whose dogs allegedly were poisoned by Faull.

McAfee earlier had fled Belize and faked a heart attack in order to return to the United States.. He never was criminally charged in Faull’s killing.