Adrian Lamo, a computer hacker best known for passing on information that led to the arrest of Chelsea Manning, has died aged 37.
In online messaging conversations, Manning confided in him, describing confidential military material Manning had sent to Wikileaks.
Wikileaks published the video of a US helicopter strike that killed seven people, including a journalist working for the Reuters news agency.
The cause of Lamoâ€™s death, confirmed to the BBC by the Sedgwick County coroner in Kansas, has not yet been made public.
On Facebook, his father Mario wrote: â€œWith great sadness and a broken heart I have to let know all of Adrian's friends and acquittances [sic] that he is dead. A bright mind and compassionate soul is gone, he was my beloved son.â€
Lamo's own record as a hacker included some high-profile targets, such as Microsoft and the New York Times.