Adrian Lamo, the computer hacker who passed on information that led to the arrest of Chelsea Manning, has died aged 37.
His father Mario broke the news of his son's death on Facebook.
“With great sadness and a broken heart I have to let know all of Adrian’s friends and acquaintances that he is dead. A bright mind and compassionate soul is gone, he was my beloved son,” Mario Lamo wrote in a post to the 2600: The Hacker Quarterly Facebook Group.
The cause of Lamo’s death, confirmed to the BBC by the Sedgwick County coroner in Kansas, is not yet known.
He was dubbed "the homeless hacker" for his habit of using public places such as coffee shops and internet cafés to carry out his cyber activities.
Adrian Lamo, the prolific hacker who turned Chelsea Manning in to the feds, has died, according to FB posts from his family. pic.twitter.com/rqQ2evsSiw— Jack Smith IV (@JackSmithIV) March 16, 2018
Most of his illicit behaviour involved breaking into computer networks and then reporting on their vulnerabilities to the companies that owned them.
One of Lamo's biggest claim to fame came when he broke into the intranet of the New York Times and added his name to their database of experts.
He also used the paper's LexisNexis account to gain access to the confidential details of high-profile subjects. He was sentenced to two years probation and ordered to pay $65,000.
The hacker hit the headlines again for reporting conversations he had with Chelsea Manning, then Bradley Manning, to the US Army.
Manning is said to have reached out to Mr Lamo, whose high-profile raids on the networks of corporate America made him a hero in some circles, and told him of his struggles as a gay soldier serving in Iraq in 2010.
Mr Lamo, who had been diagnosed with Asperger's syndrome, told the young soldier, who went by the handle bradass87, to treat their talks "as a confession or an interview (never to be published)".
In their discussions, bradass87 talked about stealing 260,000 diplomatic cables and releasing them to WikiLeaks in the hope of sparking "worldwide discussion, debates, and reforms".
The online chat began on May 21, 2010 but within four days the hacker became worried about the scale of what he was being told and reported the conversation to authorities. Hours later, Manning was arrested by military police near Baghdad.
Manning was released from military prison last year after Barack Obama commuted her 35-year sentence. She is now trying to become the Senator for home state of Maryland.
Lamo, who was called a "traitor" and the “world’s most hated hacker” by some at the time, had expressed regret for what happened to Manning.
He told the Guardian in 2011 that he thought of Manning “every day” and that "the decision was not one I decided to make, but was thrust upon me”.
He added: “Had I done nothing, I would always have been left wondering whether the hundreds of thousands of documents that had been leaked to unknown third parties would end up costing lives, either directly or indirectly."
Julian Assange, the founder of Wikileaks, tweeted on Friday that Mr Lamo was a “petty conman and betrayer of basic human decency”.