A man in the US state of Oklahoma has been handed the death penalty for the gruesome beheading of his colleague in 2014. Alton Nolen, 33, had repeatedly pleaded guilty and asked to be executed, but the judge at his trial had declined the plea.

The death penalty was recommended by a jury and accepted by Cleveland County District Judge Lori Walkley on Friday 15 December. Nolen had been found guilty earlier this year.

Nolen had been suspended from his job at the Vaughan Foods processing plant in Moore, Oklahoma when he entered the building and attacked workers. He was convicted of decapitating 54-year-old Colleen Hufford in the brutal attack.

Another colleague was critically injured in the attack, but survived.

Recordings from Nolen's hospital bed of him confessing to the attack were played at trial, including parts where he said he did not regret the attack "at all" and said "oppressors don't need to be here." His attorneys claimed that he was mentally ill and that the attacks were based on a delusional misinterpretation of the Quran. According to reports colleagues have previously said he had attempted to convert them to Islam.

One attorney had suggested that Nolen was not mentally fit to enter a plea, according to a report from the Associated Press. Earlier reports suggested that Nolen suffered from mild mental retardation and struggled as a child in school.

Nolen had attended special education classes and reportedly underwent an IQ screening which gave him an over IQ score of 69.

Though his legal team tried to suggest that he was mentally ill, prosecutors said that Nolen understood right from wrong when he attacked and killed Hufford.

According to Newson6.com, along with the death sentence, Nolen was handed three life sentences and 130 years imprisonment for assault and battery with a dangerous weapon.