An Oklahoma inmate whose execution was halted Tuesday because the delivery of a new drug combination was botched died of a heart attack, the state Department of Corrections said.
Director Robert Patton said inmate Clayton Lockett died Tuesday after all three drugs were administered.
Patton halted Lockett’s execution about 20 minutes after the first drug was administered. He said there was a vein failure.
Lockett was writhing on the gurney and shaking uncontrollably.
The planned execution later Tuesday of a second inmate was postponed.
The executions of Lockett and Charles Warner previously had been delayed after they challenged the secrecy behind the state’s lethal injection protocol. Lockett received a new lethal injection formula that included the sedative midazolam as the first in a three-drug combination.
A four-time felon, Lockett, 38, was convicted of shooting 19-year-old Stephanie Neiman with a sawed-off shotgun and watching as two accomplices buried her alive in rural Kay County in 1999 after Neiman and a friend arrived at a home the men were robbing.