Abraham Biggs, 19, took a fatal drug overdose on a live video streaming website on Wednesday.

He then posted a suicide note on another site and died several hours later, the Broward County, Florida, Medical Examiner's Office confirmed.

Mr Biggs, of Pembroke Pines, began blogging about plans to kill himself 12 hours before he was found lying dead on his bed.

His sister, Rosalind Biggs said: "When (police) came in, the webfeed stopped. So that's 12 hours of watching.

"They got hits; they got viewers; nothing happened for hours."

According to Ms Biggs, although her brother struggled with bipolar disorder he was a friendly, social, outgoing person who enjoyed spending times with his young nieces.

"It boggles the mind," she said. "We don't understand."

Wendy Crane, medical/legal death investigator from the county medical examiner's office, said Mr Biggs had died at his home from a toxic combination of opiates and benzodiazepine, a drug used to treat insomnia and depression.

His death was recorded as suicide.

She said: "He was blogging; he put a link on the blog which was linked to a webcam. He stated that he had taken an overdose of prescribed medication and later posted a suicide note.

"Throughout the day several messages were posted saying he was not moving and asking 'should we call the police?' "

She said that eventually a site administrator was contacted who called the authorities but police arrived too late to save him.

It is unclear how many people were watching through the website bodybuilding.com.

Mr Biggs, who used the screen name CandyJunkie on the bodybuilding website, posted a link from it to Justin.tv, a site that allows users to broadcast live videos from their webcams.

Police were reportedly seen on the website stream entering his room, where he lay prone, before switching off the webcam.

A spokesman for Pembroke Pines Police Department said they were investigating but declined further comment.

Justin.tv released a statement from chief executive Michael Seibel, which read: "Justin.tv staff would like to take a moment to recognise and reflect upon the tragedy that occurred within our community today.

"We regret that this has occurred and want to respect the privacy of the broadcaster and his family during this time."

A spokeswoman for Justin.tv added: "We have policies in place to discourage the distribution of distressing content and the community monitors the site accordingly.

"This content was flagged by our community, reviewed, and removed according to our terms of service."

Some users who read the blog told investigators they did not take him seriously because he had threatened suicide on the site before.

Mr Biggs's death mirrors that of Kevin Whitrick, 42, of Wellington, Telford, Shropshire, who committed suicide in March last year while being watched by others on a webcam.