A fired employee who had been trying to convert co-workers to Islam stabbed two female colleagues - beheading one of them - before an off-duty officer shot him, police have said.

Alton Alexander Nolen, who converted to Islam during a recent stint in prison, was fired from Vaughan Foods, a food processing plant in Moore, Oklahoma, on Thursday before returning to his SUV and smashing it into another vehicle.

The 30-year-old then climbed out and entered the building, attacking the first two people he saw with a knife he had used at the plant, Moore Police Sergeant Jeremy Lewis said.

After beheading Colleen Hufford, 54, and stabbing Traci Johnson, 43, Nolen was shot and wounded by off-duty sheriff's deputy and company CEO Mark Vaughan.

Nolen survived and was hospitalized. Johnson is in stable condition in hospital.

The FBI is now investigating Nolen's recent conversion to Islam to determine whether it was connected to the attack.

'Killer': Alton Alexander Nolen, 30, allegedly attacked two women after entering a food distribution center on Thursday - beheading one of them. He was eventually stopped when he was shot by an off-duty officer

The bureau will work in conjunction with the Moore Police Department to chart Nolen's background as his motives are still unclear, Fox News reported.

Authorities applauded Vaughan, an Oklahoma County reserve deputy, for his quick-thinking. He owned Vaughan Foods until it was acquired by Reser's Foods in 2011.

'This was not going to stop if he didn't stop it,' Lewis said. 'It could have gotten a lot worse.'

Sheriff John Whetsel with the Oklahoma County Sheriff's Office added in a statement: 'These were heinous criminal acts that were ended by the quick response of Oklahoma County Reserve Deputy Sheriff Mark Vaughan.

'I am extremely proud of the actions of Deputy Vaughan and I am convinced those actions saved the lives of several other employees.

'Mr. Vaughan, who serves as CEO of Vaughan Foods, was at work and when he was alerted that a man was attacking employees with a knife, Mark didn't hesitate. He quickly responded.

'Mark put an end to the threat by shooting the suspect and saving the life of a second victim who was being actively attacked by the suspect.

Heroic: Mark Vaughan, pictured above, shot the suspect multiple times to put an end to his killing spree. Mr Vaughan is the former president of the company, left, and a reserve sheriff's deputy, right

Scene: Police swarm Vaughan Foods, a food distribution center in Moore, Oklahoma, following the incident

Emotional: Employees and friends wait behind a tape for word of loved ones as police investigate on Thursday

Stopped: Police tape cordons off a black SUV the 30-year-old suspect drove to the store on Thursday

'There is every reason to believe that the lives of untold others were saved who would have been targeted by the suspect if it hadn't been for Deputy Vaughan's actions.'

Sergeant Lewis, who said he does not know why Nolen was fired, added that police are waiting until he was conscious before they move forward with charges.

He ran into the building and stabbed a woman... We can hear a lot of screaming 911 call from Vaughan Foods

On Friday, Lewis said that Nolen had been trying to convert co-workers to Islam and that local police had contacted the FBI to help investigate the man's background, KFOR reported.

Co-workers said Nolen himself had only just converted to Islam, according to News9. It is not yet known if his beliefs played a role in the attack.

There were no immediate indications of a link to terrorism, officials said.

Announcing the FBI's involvement in the case, police released a statement saying: 'After conducting interviews with Nolen's co-workers, information was obtained that he recently started trying to convert several employees to the Muslim religion.

'Due to the manner of death and the initial statements of co-workers and other initial information, the Moore Police Department requested the assistance of the FBI in conducting a background investigation on Nolan.'

Records show Nolen has a long previous criminal record including assault and battery on an officer, possession of a controlled substance and possession of cocaine with the intent to distribute.

In 2010 he was charged with assault and battery of a police officer after being pulled over for having a fake license plate.

He was discovered to be driving with a suspended license and when the officer tried to cuff him he pushed him hard in the chest and bolted.

Update: Speaking at a press conference on Friday, Moore Police Sgt. Jeremy Lewis said that the women weren't targeted - they were just in Nolen's way. He also praised Vaughan for saving other employees

Sadness: Workers stand in silence outside Vaughan Foods as they wait to leave following the grisly attack

Overwhelmed: A worker from Vaughan Foods reacts after her colleague was stabbed to death

Anxious: Employees wait in the parking lot as police continue to look into the incident on Thursday

Evacuation: Around 300 employees were in the plant at the time of the attack on Thursday afternoon

WHO IS ALTON NOLEN? OKLAHOMA SUSPECT'S LONG RAP SHEET Records show Nolen has a long criminal record. In 2006 he was charged with possession of cocaine with intent to distribute. He was only convicted in April 2011 when he pleaded guilty and was sentenced to six years with credit for time served to run concurrent with later sentences. In 2009 he was arrested after an anonymous tip that he was dealing drugs out of his sister, Paige's, apartment at the Langston University Commons complex. He pleaded guilty to possession of marijuana, obstructing an officer and resisting an officer. He was sentenced to five years deferred sentence, fined $1,200 and sentenced to 40 hours community service as well as agreeing to attend drug court. He was repeatedly sanctioned by drug court for failing to stay clean and spent three days in jail the following May and four consecutive weekends in June 2010. Then in 2010 he was charged with assault and battery of a police officer after being pulled over for having a fake license plate. He was discovered to be driving with a suspended license and when the officer tried to cuff him he pushed him hard in the chest and bolted. According to Oklahoma State Court Records, there was 'a massive manhunt involving four law enforcement agencies, two helicopters... and lasted for over 12 hours.' As part of his sentence – five years with all but the first two suspended – he was ordered to attend an anger management course. He was last released from jail in March 2013, according to records. Advertisement

According to Oklahoma State Court Records, there was 'a massive manhunt involving four law enforcement agencies, two helicopters... and lasted for over 12 hours.'

As part of his sentence – five years with all but the first two suspended – he was ordered to attend an anger management course. He was last released from jail in March 2013, according to records.

Records also reveal he has a tattoo of Jesus on his chest and praying hands on his arm.

He also has 'Assalamu Alaikum' - a greeting often used by Muslims meaning 'may peace be on you' - on his abdomen.

On Friday, 911 calls revealed the panic after he entered the building on Thursday afternoon.

'They're in the office, front office of the building. Yeah, we can hear a lot of screaming,' the caller tells the dispatcher.

'We don't know where the person went and he went through our front office, went through the shipping office and stabbed a woman in our customer service department.'

The suspect can be heard running and then three gun shots are heard, KFOR reported.

'Stay down! Stay down!' the caller tells his fellow employees.

Lewis confirmed to KFOR that the type of knife he allegedly used in the attack was the same kind used at the plant. Nolen had worked as a production line employee.

He added that the suspect and the victims were apparently not involved with each other outside of their work at the business.

'The victims had no relationship to the suspect. He is just an angry employee that acted out,' Lewis said.

Police had been called to the store around 4.15pm following a report about a fight inside Vaughan Foods. While en route, officers were told that there had been a shooting, Lewis said.

Long rap sheet: Nolen has a long criminal record including assault and battery on an officer and drug possession. In 2010, he sparked an overnight manhunt when he eluded cops trying to arrest him

Investigation: A Moore police officer helps secure a scene at Vaughan Foods. The FBI are also joining the case

'When officers arrived they approached the business as an active shooter situation. Once they entered the business they found a female deceased of stab wounds and they had a male with multiple gunshot wounds,' Lewis said.

He said the building was evacuated and searched and no other danger was found.

Employees returned to work on Friday.

'On behalf of everyone at Vaughan Foods, we are shocked and deeply saddened by the events of today,' the company said it a statement. 'Our thoughts and prayers go out to the families and friends of the team member we lost and all those affected.'