NORMAN, Oklahoma - Opening statements in the murder trial of Alton Nolen began Thursday afternoon after the jury was selected. Judge Lori Walkley told the jurors Nolen pleaded not guilty by reason of insanity.

Nolen, 33, is accused of beheading Colleen Hufford at Vaughan Foods in Moore in September 2014. He is charged with first degree murder, assault and battery with a deadly weapon, and four counts of assault with a dangerous weapon. Six victims were named.

Cleveland County district attorney Greg Mashburn began his opening statement by recapping the crime, saying Nolen "brutally and ferociously" killed Hufford after he was suspended from work the same day.

Nolen and Traci Johnson, who was severely injured but survived, allegedly worked together when he got into an argument with her. Mashburn said he told Johnson, "I beat Caucasians." The situation was brought to Human Resources and Nolen was escorted off the property.

Then Nolen went home, got a knife, and went back to Vaughn to kill certain individuals, according to the state. He was finally stopped by Mark Vaughan, who was also an Oklahoma County Sheriff's Office Reserve Deputy. Vaughan fired three rounds, putting Nolen down until police arrived.

Mashburn said Nolen claimed to be Muslim and said his religion drove him to behead anyone who oppressed him. He said Nolen even admitted to the crime to police. Mashburn told the jurors Nolen made many choices that day and had clear motivations. He asked the jury to find Nolen guilty.

Capital trial attorney Shea Smith with the Oklahoma Indigent Defense System followed up with the defense's opening statement. Smith said there is no doubt Nolan committed the beheading and injured others and asked the jury to find Nolen not guilty by reason of insanity. She said Nolen was mentally ill, and he thought what he was doing was right.

She added, "His beliefs about his religion are delusional." She mentioned that his actions do not describe the Muslim culture.

The jurors will return to the trial at 9:00 a.m. Friday.