Ross William Ulbricht, the suspected operator of the Silk Road - an anonymous online marketplace used extensively for dealing drugs and other illegal items - has been arrested by the FBI in San Francisco.
The Silk Road as it currently appears.
An FBI spokeswoman said that Ulbricht had been charged with conspiracy to traffic narcotics, following his arrest at a public library on Tuesday.
The Silk Road site, which is only accessible via the anonymous browser Tor, is also now offline, with those trying to access it being presented with a notice stating the site has been seized.
The FBI has also seized approximately $3.6m (£2.2m) worth of bitcoins, an amount it claims makes it the biggest such seizure to date.
Court papers filed in the Southern District of New York state detail how Ulbricht had generated sales of more than $1.2bn via the Silk Road, and had been involved in a money laundering operation to hide the activity.
"From in or about January 2011, up to and including September 2013, the Silk Road Hidden Website... has served as an online marketplace where illegal drugs and other illicit goods and services have been regularly bought and sold by the site's users," read the papers.
"The complainant further alleges, in part, that the Silk Road Hidden Website is designed to facilitate the illicit commerce hosted on the site by providing anonymity to its users, by operating on what is known as The Onion Router or Tor network... and by requiring all transactions to be paid in bitcoins, an electronic currency designed to be as anonymous as cash."
A second document further alleges that files on the Silk Road's server suggest Ulbricht had been willing to engage in violence to defend his interests, including evidence to suggest he hired an assassin to murder a Canadian Silk Road user who was threatening to reveal the identities of other users. However, the documents do also note that law enforcers had no record of a homicide in White Rock, British Columbia a the time.
The FBI said Ulbricht would appear in San Francisco federal court later this Wednesday, where along with the narcotics charges he'll also face charges for computer hacking conspiracy and money laundering conspiracy.