The suffering experienced by an Oklahoma inmate during his botched execution this week “may amount to cruel, inhuman and degrading treatment according to international human rights law,” a United Nations human rights official said Friday.

Rupert Colville, spokesperson for the UN High Commissioner for Human Rights, made the comments while speaking to media in Geneva.

The state used untested drugs to execute Clayton Lockett by lethal injection on Tuesday. Witnesses describe seeing Lockett “writhe in pain,” clench his teeth and struggle. He died of a heart attack 43 minutes after the first injection started.

According to details released by the Oklahoma Department of Corrections, in the morning Lockett had cut himself and prison officials tased him.

According to the documents, an IV was inserted into Lockett’s groin, where he received a trio of drugs, but 11 minutes after the second two drugs were injected, officials saw that something had gone wrong and closed the blinds so witnesses couldn’t see. The doctor said Lockett’s vein had collapsed, and that the drugs had been absorbed by tissue or leaked out. The execution was called off, and Lockett was pronounced dead of a heart attack minutes later.