A worker who had recently tried to convert colleagues to Islam beheaded one of them in a knife rampage after being dismissed from his job in Oklahoma state, according to US police.
The suspect, identified as 30-year-old Alton Nolen, attacked another colleague with the knife before being shot by the Oklahoma food-distribution firm's head - who was hailed a hero by police.
Nolen, who survived and was in hospital in a stable condition, appeared to have chosen his victims at random, police said of Thursday's incident, and there was no immediate indication of a link with terrorism.
"Nolen went to the parking lot, then drove his vehicle to the front of the business ... he then entered the main entrance," Jeremy Lewis, police spokesman, said in the city of Moore on Friday.
"Nolen encountered and killed Colleen Hufford with a knife. During the attack, Nolen severed the victim's head."
The second, wounded colleague was admitted to hospital and was in a stable condition.
"After conducting interviews with Nolen's co-workers, information was obtained that he recently started trying to convert several employees to the Muslim religion," the spokesman said.
Because of the nature of the crime local police called in the Federal Bureau of Investigation, he said.
It comes after a series of beheadings of Western captives by self-declared jihadists in the Middle East and Algeria, but US officials have not confirmed any link to the Oklahoma case.
A spokesman for the Islamic Council of Oklahoma said Muslims were "shocked, horrified and saddened".
Commenting on reports that Nolen had recently converted to Islam, Sheryl Siddiqui, the Islamic Council's spokeswoman, said: "He was not known to any of the leadership in Oklahoma mosques.
"We do not have any confirmation of his conversion either in prison or out in the community. Muslims are supporting law enforcement efforts to perform their due diligence and seek justice in this case."
The Washington DC-based Muslim Public Affairs Council (MPAC) also said it was "horrified".