Internet hackers yesterday took over the US Sentencing Commission's website, in anger over the death of cyber-legend and internet freedom advocate Aaron Swartz.
Anonymous, a web of loosely connected "hacktivists" which rails against controls on internet freedom, appears to be responsible.
The commission's website home page was replaced with a statement from the group saying they, "have been watching and waiting."
After decrying the state of the American justice system, it continues: “Two weeks ago today, Aaron Swartz was killed. Killed because he faced an impossible choice. Killed because he was forced into playing a game he could not win — a twisted and distorted perversion of justice — a game where the only winning move was not to play.”
Swartz, 26, gained fame for his involvement in the social news site Reddit, and in the development of RSS feeds.
He killed himself a fortnight ago while facing trial for hacking a university's trove of online journals, intending to release them for free online.
Though he had a history of depression, his family and friends say the threat of 30 years in prison motivated the suicide, and at a memorial service last weekend, supporters called for the prosecutors to be held accountable for their actions.
It has since emerged he was offered a plea deal of six months, and officials have insisted they did not over-reach in their pursuit of Swartz.
The commission is an independent agency of the judicial branch involved in sentencing.
The hackers also said they had infiltrated several government computer systems and copied secret information they threatened to make public.
Saying the information was like a nuclear weapon, the group said it had "enough fissile material for multiple warheads" which it would launch against the justice department and organisations linked to it.
By late Saturday morning, the website was offline, but cached versions could be found where the message appeared.
The FBI's Richard McFeely, executive assistant director of the Criminal, Cyber, Response, and Services Branch, said: "we were aware as soon as it happened and are handling it as a criminal investigation. We are always concerned when someone illegally accesses another person's or government agency's network."