Ilya “Dutch” Lichtenstein was a 30-year-old tech entrepreneur living in New York in 2018 when he published a blog post detailing his thoughts on what was holding cryptocurrencies back from achieving “mass adoption.”

In the post, the self-described “tech entrepreneur, explorer, and occasional magician” wrote that there were “four recurring usability nightmares of blockchain.”

Number one on that list of nightmares, according to Lichtenstein? Security.

“The biggest threat to mass adoption is without a doubt, security,” Lichtenstein wrote. “People are terrified of hackers and malware.”

But law enforcement officials say that Lichtenstein and his wife, Heather Morgan, were sitting on more than $4.5 billion in cryptocurrency stolen during the 2016 hack of Bitfinex, a virtual currency exchange, according to a Department of Justice press release on Tuesday. The couple was arrested in Manhattan on Tuesday.

So far, the DOJ says it has seized more than $3.6 billion in cryptocurrency from the millennial couple. According to Deputy Attorney General Lisa O. Monaco, it’s the department’s largest financial seizure ever.

The seizures “show that cryptocurrency is not a safe haven for criminals,” Monaco said in the press release. “In a futile effort to maintain digital anonymity, the defendants laundered stolen funds through a labyrinth of cryptocurrency transactions.”

For her part, Morgan is a self-professed “serial entrepreneur” with a Twitter following of almost 20,000. On the side, she is a rapper and streetwear fashion designer that goes by the stage name Razzlekhan.

According to her website, Morgan’s art as Razzlekhan “often resembles something between an acid trip and a delightful nightmare.” She also described it as “definitely not for the faint of heart or easily offended. Razz likes to push the limits of what people are comfortable with.”

The 31-year-old also served as a Forbes contributor, with at least 55 articles written for the website between July, 2017 and September, 2021. In 2019, Morgan penned an essay for Forbes in which she offered her best advice to burnt-out executives and entrepreneurs: “Try rapping,” Morgan wrote.

In a statement to Fortune, a Forbes spokesperson said that Morgan “was a Forbes contributor up until September 2021 and was never a Forbes employee.”

Lichtenstein and Morgan got engaged in 2019, according to Lichtenstein’s Facebook page. Together, they founded Endpass, a tech startup that uses Artificial Intelligence to automate identity verification while proactively detecting fraud.

According to Lichtenstein’s Medium post, the couple created Endpass as a solution to the security risks he said was “standing in the way of [crypto’s] massive market growth.”

But while Lichtenstein and Morgan were co-founding a company designed to help bolster the security of cryptocurrencies in order to help it achieve mainstream appeal, the DOJ alleges that behind closed doors, they were quietly laundering the proceeds of over 100,000 Bitcoin stolen in the 2016 Bitfinex hack.

The couple were not charged in the hack at the time, or known to be involved.

Prosecutors say Lichtenstein transferred out millions of dollars of stolen funds through Bitcoin ATMs. They allege that the funds were then used to purchase gold and non-fungible tokens, as well as Walmart gift cards and other personal items.

In a tweet sent on Jan. 15 from Manhattan, just weeks before her arrest, Morgan wrote, “Good guiding compass to live by: How much of a POSITIVE IMPACT does your life have on others, including society & nature?”

Lichtenstein and Morgan are scheduled to make their first appearances in federal court in Manhattan later this afternoon.

Fortune was not able to reach either Lichtenstein or Morgan for comment.