McALESTER, Okla. (AP) — The director of the Oklahoma Department of Corrections says an inmate whose execution was halted because the delivery of a new drug combination was botched has died of a heart attack.

Director Robert Patton says 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 says 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.

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