An autopsy done on Oklahoma death row inmate Clayton Lockett, revealed that drugs, not a heart attack, was in fact what killed him.

The Associated Press reported that on Thursday, the results of the autopsy were released and the concluded that the inmate actually did die from the lethal drugs in the problematic execution that took place in April.

Department of Corrections Director Robert Patton initially said that Lockett died of a massive heart attack 43 minutes after his execution was halted because the lethal injection of three drugs were botched.

According to the Oklahoman, the Texas medical examiner’s autopsy report stated the opposite.

“It is our opinion that Clayton Derrell Lockett, a 38-year-old black male, died as the result of judicial execution by lethal injection,” the report released by the Oklahoma Department of Public Safety read.

On the day of his execution, a doctor injected Lockett with the first drug at 6:23 p.m. and administered the other two drugs several minutes later. Eyewitnesses said that Lockett, however, remained conscious and began to convulse and struggle on the gurney.

The incident was investigated and the Court of Criminal Appeals agreed not to schedule any executions in the state for several months.