Michael Marin, 53, was found guilty of arson by a jury in Maricopa County Superior Court. He appeared shocked and closed his eyes as the verdict was read before appearing to put something in his mouth and wash it down with liquid in a plastic water bottle.
In the shocking court room video, he then fell to the floor a few minutes later in convulsions. Mr Marin was taken to a hospital in Phoenix, Arizona, where he was pronounced dead.
© Fox NewsLast resort: After being found guilty of burning down his own home and facing years in jail, Michael Marin appeared to swallow a substance in the Arizona
When Marin's trial began in May, prosecutors said he could face 16 years in prison if he was convicted.
Marin burned down his Phoenix mansion on July 5, 2009 after it failed to sell at a charity auction.
Fire Department investigators determined the fire was deliberate after finding several points of origin throughout the sprawling 6,600 sq ft home with four garages.
Marin later told authorities that he had escaped after setting the fire by climbing from the second floor using a rope ladder and wearing a scuba-diving suit, according to Fox.
© Phoenix Fire DeptDestruction: Marin had tried to auction off his mansion in Arizona but had no bidders
Prosecutors claimed Marin set fire to his house in desperation because he could no longer pay the mortgage.
Toxicology tests would be carried out on the 53-year-old's body along with the water bottle he drank from.
Marin, a father of four and grandfather of two, attended Yale Law School. He was an ex-Wall Street trader who enjoyed collecting art including Picasso sketches and described himself as a 'careful thrill seeker' to the Phoenix New Times after scaling Mount Everest and trips into the jungles of south-east Asian.
He has all the markers like Yale and Wall Street, and even enjoyed his art sketches and a 'careful thrill' on Mount Everest. He must have been a very good boy indeed as he came prepared as all good scouts would if they know their oath.