A man accused of beheading a co-worker at the food processing plant where they worked must stand trial on a first-degree murder charge, an Oklahoma judge said Friday.

Alton Nolen, 31, could face the death penalty if convicted in the September 2014 attack at the Vaughan Foods processing plant in Moore, an Oklahoma City suburb. Nolen is accused of beheading Colleen Hufford and injuring another employee.

Another co-worker who witnessed the attack, Gary Hazelrigg, told Special Judge Steve Stice at Nolen's preliminary hearing on Friday that Nolen charged into an office carrying a large knife and immediately attacked Hufford.

"In no more than a second or two, the man pulled her forehead toward him and made a vicious cut across her throat with the knife," Hazelrigg testified.

Hazelrigg said another co-worker attempted to stop Nolen but was unable to subdue him.

Investigators have said Nolen had just been suspended from his job when he walked into the company's administrative office and attacked the woman, severing her head. He then repeatedly stabbed co-worker Traci Johnson, authorities say, before he was shot by Mark Vaughan, a reserve sheriff's deputy and the company's chief operating officer. Johnson survived the attack.

In October, a judge found Nolen mentally competent to stand trial, rejecting defense attorneys' claims that Nolen was intellectually impaired. He has pleaded not guilty.