Abraham Biggs, a college student at South Florida, committed suicide by overdosing on opiates and benzodiazepine, in front of a live web audience.
Before he died, members of his audience encouraged him, questioned his method, and tried to tell him to stop.
Biggs, 19, died Wednesday in his home, said Wendy Crane, an investigator with the Broward County medical examiner's office.
Authorities say the Broward Community College student is not the first person to commit suicide with a webcam rolling.
It's unclear how many people were watching through the Web site bodybuilding.com. Someone finally notified a site moderator, who pinpointed Biggs' location and called police, but they arrived too late to save him, Crane said.
Biggs, who used the screen name "CandyJunkie" on the bodybuilding Web site, started blogging about plans to kill himself 12 hours before he was found lying dead on his bed. He posted a link from bodybuilding.com to Justin.tv, a site that allows users to broadcast live videos from their webcams.
Some users who read the blog told investigators they did not take him seriously because he had threatened suicide on the site before.
But Biggs' family was infuriated that neither viewers nor the site acted sooner to save him.
"When (police) came in, the webfeed stopped. So that's 12 hours of watching," said his sister, Rosalind Biggs, who said her brother struggled with bipolar disorder. "They got hits, they got viewers, nothing happened for hours."
Rosalind Biggs described her brother as a friendly, social, outgoing person who struck up conversations with Starbucks baristas and enjoyed taking his young nieces to Chuck E. Cheese.
"It boggles the mind," she said. "We don't understand."
Authorities could not immediately verify the authenticity of a video posted online that shows a gun-wielding officer entering a bedroom where a man is lying on a bed, facing away from the camera. The officer peers over to look at the man, then begins to examine him as the camera lens is covered. The video matches Crane's description of events.
Condolences poured in to Biggs' MySpace page, where the mostly unsmiling teen is seen posing in a series of pictures with various young women. On justin.tv, his alias was "feels_like_ecstacy."
In a statement, Justin.tv CEO Michael Seibel said: "We regret that this has occurred and want to respect the privacy of the broadcaster and his family during this time."
The Web site declined to release information on how many people were watching the broadcast. The entire site had 672,000 unique visitors in October.
Messages left with the bodybuilding Web site were not immediately returned Friday.