Islamabad, Pakistan (CNN) -- The detention of a U.S. Embassy employee after two shooting deaths in the Pakistani city of Lahore last month has prompted urgent action both at home and abroad: a Justice Department criminal probe of the killings and a fence-mending diplomatic mission to the volatile Asian nation by a top American senator.
Justice officials were cautious and noncommittal about whether the probe could eventually lead to any charges against Raymond Davis. Spokeswoman Alisa Finelli said, "It's our practice to conduct criminal investigations of such incidents, and we intend to follow that practice here, considering all the facts and relevant laws."
Senator John Kerry, chairman of the Senate Foreign Relations Committee, visited Pakistan to pass along "our deepest sorrow for the loss of life" as he and other American officials underscored the U.S. position that Davis has diplomatic immunity under an international treaty and should be released.
Many Pakistanis want the man to remain incarcerated in Pakistan and face justice in its courts.
The senator -- who visited Lahore on Tuesday and Islamabad and Rawalpindi on Wednesday -- left the country later Wednesday after conferring with officials.
He delivered a statement before he departed, saying he was "encouraged" with the "excellent" visit devoted to tackling the fallout of the "tragic incident."
He said everybody "talked about their willingness to work together, in unison, in order to put the incident of Lahore behind us, to find a way not to overlook it, to give it meaning, but to use it as a building block so that we all learn the lessons of what happened there.
"I look forward in the next few days, hopefully, to finding ways that we all agreed on, that we can find in order to resolve this issue that's in front of us."
Davis said he was attacked by the two men as he drove through a busy Lahore neighborhood, according to the U.S. Embassy in Pakistan.
Lahore Police Chief Aslam Tareen has rejected Davis' claim that he shot the men in self-defense, telling reporters, "It was clear-cut murder."
Tareen acknowledged the two men were armed and that one of them pointed his gun at Davis. However, he said, the man didn't shoot, because "all the bullets were in their chamber."
A police report submitted in court appears to contradict that assertion, saying that the chambers of both the victims' pistols were empty.
The report cites witnesses as saying Davis first fired at the victims from inside his car, then stepped out and fired twice at the back of one of the victims.
On Wednesday, a U.S. official who has seen the first report from the Lahore police following the shooting incident said the report indicates it was an attempted robbery.
According to the official, who spoke on condition of not being identified, the initial police report mentions that two Pakistanis were robbed earlier in the day by the two men killed in the Davis shootings. In addition, the U.S. official said, the cell phones of the robbery victims were found on the bodies of the two men who were shot, and the robbery victims provided statements implicating the two dead men.
The U.S. official also said Davis shot only from inside his vehicle.
Meanwhile, a senior State Department official separately confirmed the details in the initial police report about the two Pakistanis being robbed earlier in the day by the two people killed in the Davis shootings.
Davis' arrest has strained relations between the United States and Pakistan, a key ally in the war against al Qaeda and the Taliban in neighboring Afghanistan, and many Pakistanis are outraged by the incident. During several protests earlier this month, hard-line Pakistani clerics condemned the shootings and demanded the government not release Davis to the U.S. government.
Davis has been detained since the shooting on January 27, an incarceration U.S. officials call illegal.
He is a contractor for the group Hyperion Protective Consultants LLC, and was attached to the U.S. Embassy contingent in Pakistan as a "technical and administrative official," according to American officials, who say he falls under the label of "diplomat."
Under international agreements, people carrying diplomatic passports are granted diplomatic immunity, the State Department says, and Davis was carrying such a passport.
The United States says Davis was assigned to the U.S. Embassy in Islamabad but was working at the U.S. Consulate in Lahore at the time of the shootings.
Kerry met with Prime Minister Yusuf Raza Gilani and other Pakistani officials on Wednesday, Gilani's office said in a news release.
Gilani -- who said it is "imperative" that the Davis matter "must not be allowed" to harm bilateral ties and the fight against terror -- called Kerry a "known friend of Pakistan" and noted that the senator wants an "early resolution" of the matter.
Gilani said his country's superior court has "taken cognizance of the case" and ordered that the question of immunity -- "if it arises" -- be determined by the court, the news release said. He also said that the "remorse and regret" shown by the United States over the deaths "should be considered to cool down the rising temperatures."
The Punjab provincial government has had control of the Davis case. The Pakistani federal government apparently never went to the authorities there to raise the issue of his release under diplomatic immunity.
That's partly because there continues to be confusion over Davis' diplomatic status and partly because of the outrage toward the United States sparked by the killings and by U.S. policies in the region.
Now the case is in Punjab courts.
"There's been a bit of a breakdown between the federal and provincial government." said Pakistani analyst Mosharraf Zaidi. "It's a political minefield."
Pakistanis enduring stress, indignity and conflict amid the war on terror and the country's economic and infrastructural problems want something in return for Davis' release, Zaidi said.
Kerry's respectful visit to Pakistan and the announcement of a Justice probe is "a good start. It reflects what the U.S. is all about," he said.
"He expressed regret," said Zaidi, saying it was the first time any remorse or condemnation was heard, and that is giving Pakistanis confidence that Americans don't think Pakistani life is cheap.
Last week, a Pakistani court ordered Davis to remain in custody for 14 more days, and a hearing will be held on the case later this month.
A separate hearing will be held Thursday on a petition calling for his immediate release on the grounds he is covered under diplomatic immunity.
"From our standpoint it is not a matter of dispute, certainly not a matter that should be resolved by courts in Pakistan," said U.S. State Department spokesman P.J. Crowley. "That said, there will be a hearing in court tomorrow and we will present a petition to the court that he, in fact, has diplomatic immunity ... and should be released."
Mark Quarterman, director of the Program on Crisis, Conflict, and Cooperation of the Center for Strategic and International Studies, said this incident is occurring against the backdrop of a negative perception in Pakistan toward the United States.
Pakistanis think the United States is pushing the country around and that intelligence and security agencies are acting freely there, with the Pakistani government blind to that reality, he said.
In addition, it's unclear exactly what role Davis has in the embassy, which has aggravated suspicions and conspiracy theories toward the United States, Quarterman said.
So the government has been reluctant to accede to U.S. wishes and release Davis, and it is satisfied to have his case in the courts, saving politicians from making unpopular decisions, he said.
"This is touching one of the most sensitive nerves in U.S.-Pakistani relations," Quarterman said. "There's a drama being played out now because of the potential domestic consequences."
One former senior intelligence official who asked not to be named believes that Davis could be a security contractor or an employee of an intelligence service.
The fact that he was armed and proficient with firearms indicates "he's got some relationship with our intelligence services," the official said.
The source -- who doesn't have direct knowledge of the case but is familiar with issues involving diplomats and security -- said the United States never wants its diplomatic personnel taken and will do what they can to have them released.
"We really care about this guy," the source said. "The response of the U.S. government has been particularly strong. That to me is an indication that he has some well-defined relationship to the U.S. government."
There are people in embassies located in hot spots where particular expertise, specialties and resources are required, the source said. Sometimes there are intelligence people in those places because they have close relations with the host country's intelligence service.
"Those people are particularly important," the source said.
Davis has a diplomatic passport and therefore has diplomatic immunity, a status respected by nations across the world, the source said.
Pakistan's behavior is "pretty outrageous" and the United States is "irritated with this," the former intelligence official said.
Pakistani officials are behaving this way perhaps because they think the man is more directly related to specific U.S. intelligence activities than Washington has acknowledged, the source said.
As for the question of whether diplomats customarily carry guns, Crowley told reporters on Wednesday that "there are people with diplomatic status in countries around the world who are authorized to carry weapons."
CNN's Reza Sayah, Nasser Habib, Terry Frieden, Pam Benson, Elise Labott and Joe Sterling contributed to this report