Updated

An Oklahoma man was convicted Friday of first-degree murder in the 2014 beheading of his co-worker at a food processing plant.

Jurors deliberated for about two hours before finding 33-year-old Alton Nolen guilty in the death of 54-year-old Coleen Hufford.

The jury also convicted Nolen of assault and battery with a deadly weapon for attempting to behead a second co-worker at the Vaughan Foods plant in Moore, a suburb of Oklahoma City. Prosecutors have said they would seek the death penalty.

Investigators said Nolen had just been suspended from his job when he walked into the company's administrative office and attacked Hufford. Authorities said Nolen stabbed another co-worker, who survived, before he was shot by a company executive.

Defense attorneys argued that Nolen is mentally ill and didn't know his actions were wrong, with one attorney saying that their client had created his own religion in his mind that "doesn't make sense to anyone else." But prosecutors said Nolen knew right from wrong before he attacked Hufford.

Nolen had repeatedly tried to plead guilty and asked to be executed, but Cleveland County District Judge Lori Walkley declined to accept his plea. One of Nolen's attorneys had questioned whether his client was mentally competent to enter a guilty plea.

At a 2016 hearing, Nolen told Walkley that he would only accept a death sentence, not life in prison with or without the possibility of parole.

But the judge reminded Nolen repeatedly that if he pleaded guilty and waived his right to a jury trial, the decision to sentence him to death or life in prison would be up to the judge, not the defendant.

The Associated Press contributed to this report.