Swartz, 26, left no note before his apparent Friday morning suicide inside the seventh-floor apartment on Sullivan St., police sources said. His body was taken to the city medical examiner for an autopsy.
His death came two years to the day after his arrest for breaching a computer network to download millions of pages of papers and documents from the Massachusetts Institute of Technology.
His trial on federal charges that carried a possible 35-year prison sentence was set to begin in February.
Swartz was a well-known computer prodigy who helped create RSS at age 14 and later co-founded the social news website Reddit.
He also directed Demand Progress, an internet group that campaigns against web censorship.
“He was brilliant, and funny,” said friend Larry Lessig, a Harvard Law professor, in a blog post. “A kid genius. A soul, a conscience, the source of a question I have asked myself a million time: What would Aaron think?”
In addition to severe financial woes caused by his legal fight, Swartz head written about his struggles with depression.