Lockett died April 29, minutes after the execution was halted. Officials said at the time that he appeared to have had a heart attack, but an autopsy ordered by Gov. Mary Fallin later found he was killed by the execution drugs.
News media representatives, who reported seeing Lockett apparently trying to talk and writhing in pain, did not witness Lockett's death. Sixteen minutes into the execution, officials lowered the blinds and escorted journalists out.
The report by the state Department of Public Safety said those in the death chamber disagreed on Lockett's reactions later in the procedure.
"Four reported that Lockett did not move, one reported he moved slightly and the last recalled a more aggressive movement," the report states.
Oklahoma, which had planned to put a second man to death the same night, has postponed all executions. The moratorium is currently set to expire early next year.
In Lockett's case, officials decided to use an IV line to the femoral vein in his groin after being unable to find any suitable arteries or veins in his limbs. But a doctor determined after the blinds were closed that the drugs were being injected into muscle tissue and tried to reset the line, the report said.
The report made a number of recommendations. They included using at least two IV lines.
The governor should be notified that an execution might have to be stopped if finding a place to insert the lines takes more than an hour, the report said.
Another recommendation calls for a backup supply of drugs. On April 29, the prison had only enough for Lockett and a second man scheduled to be executed.
Lockett was sentenced to death for killing Stephanie Neiman, 19. Neiman was shot and buried alive in 1999 after she interrupted a home invasion in Perry, Okla.
Notable deaths of 2014 [PHOTOS]