Not giving up:

Pakistan: Ambassador Asks for Release of American

By THE ASSOCIATED PRESS

Published: February 7, 2011

The American ambassador pressed the Pakistani president on Monday to release an American official who Washington said was detained illegally after he shot and killed two men in Lahore. Ambassador Cameron Munter met with President Asif Ali Zardari in Islamabad after repeated American demands for the release of the American, identified as Raymond Allen Davis...

http://www.nytimes.com/2011/02/08/world/asia/08briefs-Pakistan.html

Mystery Over Detained American Angers Pakistan
By JANE PERLEZ;
Ismail Khan contributed reporting from Peshawar, Pakistan, Waqar Gillani from Lahore, and Eric Schmitt from Washington, New York Times, February 8, 2011

Two things from the above....

The U.S. really really is not willing to let this go, for whatever reason:

....The Obama administration insists that Mr. Davis is protected by diplomatic immunity under the Vienna Conventions and that he must be released from custody. He was unlawfully seized on the street by the police after the shootings, the administration says, and should have been allowed to return to the American Consulate in Lahore in conformity with diplomatic protection.

The United States has warned Pakistan that if Mr. Davis is not released, a much sought-after state visit by President Asif Ali Zardari to Washington, planned for the end of March, could be jeopardized and badly needed financial assistance could be cut.

Last weekend on the sidelines at a conference in Munich, Secretary of State Hillary Rodham Clinton told the Pakistani Army chief, Gen. Ashfaq Parvez Kayani, that Mr. Davis was being held illegally and must be freed, a senior American official said.

American officials said they were concerned for the safety of Mr. Davis, who is being held by the law enforcement authorities of Punjab Province, an area that is becoming increasingly radicalized by Islamic militants....

They dug up some answers to the question "who is Raymond Davis?":

Mr. Davis spent 10 years in the American military, starting with basic training at Fort Benning, Ga., in 1993. He moved to special warfare training with the Third Special Forces Group at Fort Bragg, N.C., in 1998, and left the Army in 2003. His only overseas posting, according to his Army service record, was a six-month stint as a member of a United Nations Peacekeeping force in Macedonia in 1994.

After leaving the military, Mr. Davis apparently decided to take advantage of the boom in the military contracting business. He and his wife, Rebecca Davis, set up Hyperion Protective Services in 2006 in Nevada, a company that appears to have sought government contracts for security services, according to company filings in Nevada.

The company does not appear to have won big contracts, and may have been in the business of offering just Mr. Davis’s services, according to a former Special Forces officer who reviewed the company filings.

Mr. Davis arrived in Pakistan in late 2009, according to his visa application from the Ministry of Foreign Affairs. That document described his rank as “administrative and technical staff.”

His first assignment was apparently in Peshawar, a city on the edge of the tribal areas. A Pakistani who worked in the house where Mr. Davis stayed remembered him as a generous tipper who left several hundred dollars for each of the staff members when he left last year.

The article also goes over the various versions of "what happened at Mozang?" including things like the post mortem of bullets in the backs of both victims.