The New York Times has more information about circumstances:
Aaron Swartz, a wizardly programmer who as a teenager helped develop code that delivered ever-changing Web content to users and later became a steadfast crusader to make that information freely available, was found dead on Friday in his New York apartment.
He was 26.
An uncle, Michael Wolf, said that Mr. Swartz had apparently hanged himself, and that Mr. Swartz’s girlfriend had discovered the body.
The New York Times has more information about circumstances: