Clayton Lockett - a death row inmate in Oklahoma - died Tuesday of a heart attack after officials halted his execution due a new drug mixture that left him writhing in the gurney.
Sources confirm that Lockett went unconscious after about 10 minutes and then started clenching his teeth and breathing heavily three minutes after that.
The blinds were then lowered to prevent the witnesses from seeing anything further, at which point the state's top prison official called a stop to the proceedings.
"It was a horrible thing to witness. This was totally botched," said Lockett's attorney, David Autry.
He added that it was clear from the outset that the execution was handled poorly.
"They should have anticipated possible problems with an untried execution protocol," Autry said. "Obviously the whole thing was gummed up and botched from beginning to end. Halting the execution obviously did Lockett no good."
In response to this incident, Governor Mary Fallin ordered a 14-day stay of execution for an inmate who was scheduled to die two hours after Lockett.
The execution began at 6:23 p.m., when officials began administering the drug midazolam. A doctor declared Lockett to be unconscious at 6:33 p.m. and Lockett was declared deceased at 7:06 p.m.
The American Civil Liberties Union of Oklahoma called for an immediate moratorium on state executions.
"This evening we saw what happens when we allow the government to act in secret at its most powerful moment and the consequences of trading due process for political posturing," said ACLU executive director Ryan Kiesel.