Islamabad,  Pakistan (CNN) -- The American accused of killing two Pakistani men isn't a diplomat, as U.S. officials have said, but rather a CIA contractor in the country providing security for CIA officers, a U.S. government official said Monday.





The revelation that Raymond Davis was working for the U.S. intelligence agency when he shot two men -- one of them in the back, according to Lahore police -- is a dramatic twist in a case that has already inflamed hard-line clerics and an angry public that wants the American tried in a Pakistani court.





In protests since Davis' arrest last month, hard-line Pakistani clerics have condemned the shootings and demanded that the government not release the American.





Despite the revelation of Davis' true line of work, U.S. officials on Monday renewed their argument that he enjoys diplomatic immunity and must be released.





U.S. officials notified Pakistan that Davis had been posted to the U.S. Embassy in Islamabad in January 2010, U.S. officials said. Pakistan's only recourse under international law is to order Davis out of the country, according to a senior U.S. official who briefed reporters on background Monday.





"Any other form of action, including a judicial action or any other proceeding, is inconsistent with his status," the official said.





Davis was jailed January 27 after fatally shooting two men who pulled up to him on a motorcycle in a bustling Lahore neighborhood.





U.S. officials and Lahore police said Davis told them he shot the men in self-defense. Evidence showed the two men may well have been robbers, according to police who found cash and cell phones linked to a robbery reported earlier that day.





But Lahore's police chief, Aslam Tareen, has said witnesses told police that Davis kept firing, even when one of the men was running away.





"It was clear-cut murder," Tareen told reporters.





That Davis was working for the CIA as a contract employee seems to explain the assortment of gear Lahore police reported finding in his rental car following his arrest.





According to a Lahore police report, Davis' car contained 9mm pistol, five ammunition magazines, two cell phones, an infrared light, a digital camera, a telescope, a long-range wireless set and a survival kit.





While acknowledging that Davis is a CIA contractor, the U.S. official said that Davis is not a case officer or paramilitary officer.





"Davis is a protective officer, someone who provides security to U.S. officials in Pakistan. Rumors to the contrary are simply wrong," the official said.





The  U.S. official added "any suggestions  that he was conducting covert operations  or personally leading efforts to target militant groups is  wrong."





But the  official said Davis could have been providing security for  CIA officers  who were engaged in covert operations





Davis is part  of the agency's "global response staff," which is responsible for protecting  the safety of CIA operatives in other  countries.





He was doing "advance work," scouting areas of Lahore at the time of the shooting, the official said. Davis' role required him to "know the environment."





He provided all  facets of security for case workers including  surveillance detection,  route surveillance and protection in potentially hostile environments, said the  official.





The  36-year-old Davis is a former member of the  U.S. Army special forces and had  been employed by security firm XE Services, previously known as  Blackwater.





Davis began  working for the CIA nearly 4 years ago. He was assigned  to Pakistan in  late 2009. He was living with other security personnel at  a safehouse  in Lahore before  the shooting incident.





Until Monday, U.S. officials had described Davis only as an employee who was attached to the U.S. Embassy in Islamabad and who was working at the U.S. Consulate in Lahore at the time of the shootings.





Formally, they continue to describe him only as a member of the "technical and administrative staff" of the embassy.





The U.S. government has had ongoing conversations with Pakistan
What did Davis provide? What should Pakistan do? Where is he being tried? Who did he supposedly murder? What is the American accused of?
security to U.S. officials in Pakistan. order Davis out of the country, Pakistani court. two Pakistani men killing two Pakistani men
question: What did Davis provide?, answer: security to U.S. officials in Pakistan. | question: What should Pakistan do?, answer: order Davis out of the country, | question: Where is he being tried?, answer: Pakistani court. | question: Who did he supposedly murder?, answer: two Pakistani men | question: What is the American accused of?, answer: killing two Pakistani men