A Kuwaiti security officer said the suspect, Sami al-Mutairi, 25, was not working alone. And the Interior Ministry, in its statement, said he acknowledged following the ideals of Osama bin Laden's al Qaeda terror network.
Al-Mutairi was arrested at the border with Saudi Arabia as he tried to flee and extradited to Kuwait, the ministry said. His weapon and some ammunition was found at his workplace, according to the statement. It did not say where he worked.
The ministry statement said al-Mutairi became a suspect "in the first hours after the crime was committed."
The security officer, speaking on condition of anonymity, said al-Mutairi was arrested by Saudi border guards Wednesday. The official said he was a Kuwaiti civil servant and the prime suspect, but that he "had partners, maybe two."
John Moran, spokesman for the U.S. Embassy, said the United States hoped "the investigation will move rapidly to apprehend those responsible for this crime and determine if they have ties to any larger organization. We call on the government to do everything in its power to protect our citizens from terrorist attack and to prevent any further tragedies."
The shooting was the first assault on U.S. civilians in Kuwait and the third on Americans since October in the oil-rich emirate, where pro-American sentiment is usually strong and where thousands of U.S. troops are assembling ahead of a possible war on Iraq.
The U.S. Embassy said it was urging Americans to be alert to their surroundings. About 8,000 American civilians live in Kuwait, in addition to 17,000 personnel stationed at the main U.S. military bases here and thousands of other troops who come for regular exercises.
In Tuesday's attack, a gunman hiding behind a hedge ambushed the sport utility vehicle carrying two civilian contractors working for the U.S. military, killing one and critically wounding the other. The attack took place at a stoplight about 3 miles from the U.S. military's Camp Doha, which is 10 miles west of Kuwait City.
One of the victims, David Caraway, was in stable condition Wednesday at al-Razi hospital in Kuwait City. His co-worker Michael Rene Pouliot, 46, was killed.
Pouliot was a civilian contractor with Tapestry Solutions software development company working for the U.S. military.
"Everyone is saddened by this tragedy," company spokesman Chris Wahl in San Diego told CBS News.
A wreath-laying ceremony was planned Thursday at the site of the shooting, to be followed by a private memorial service on the military base where the two victims worked.
Kuwait's crown prince and prime minister, Sheik Saad Al Abdullah Al Sabah, sent letters of condolences to President Bush condemning the "terrorist act," the state-run Kuwait News Agency said.
Small, oil-rich Kuwait was liberated in 1991 from a seven-month Iraqi occupation by a U.S.-led coalition, and depends on Washington for protection. As U.S. forces pour into the emirate, it could become a launch pad for any war on Iraq.
On Oct. 8, two Kuwaiti Muslim fundamentalists opened fire on Marines taking a break from war games on the island of Failaka, killing one and injuring another. Other Marines shot dead the assailants, who reportedly had links to the al Qaeda terror network blamed for the Sept. 11, 2001 attacks on the United States.
A policeman later described as "mentally unstable" also shot at two U.S. soldiers in their civilian car on a highway on Nov. 21.
Kuwaiti officials have described the attacks as isolated incidents, distancing themselves from any deeper al Qaeda presence. Scores of Kuwaitis have fought with Muslim extremists in Afghanistan, Chechnya and Bosnia.