Hacker Adrian Lamo has died at age 37, according to ZDNet and a Facebook post from his father. The circumstances of Lamo’s death are unknown, but a coroner in Sedgwick County, Kansas, reportedly confirmed the news.

Lamo was known in the early 2000s for hacking a number of company networks, including that of The New York Times Company. Sometimes dubbed the “homeless hacker” for his nomadic life, he pled guilty in 2004 to breaching the Times’ internal network and running up tens of thousands of dollars in search fees on its Lexis-Nexis account. Before that, he warned several other companies of security flaws, including WorldCom and Microsoft.

More recently, however, Lamo was known for alerting the Army after whistleblower Chelsea Manning confided in him about leaking classified material to WikiLeaks. Lamo said he acted out of a sense of “duty,” but later expressed some regret for the decision, although he stood by it in later interviews. “A bright mind and compassionate soul is gone,” wrote Lamo’s father on Facebook.