Officers were called to the house of Christianson's family in the early morning. Christianson was outside during the standoff, and all seven houses on the cul-de-sac were evacuated.

Bontz said Christianson never pointed the rifle at police.

He could face a charge of failure to comply with orders from emergency personnel, Bontz said.

Christianson is stationed at Camp Pendleton, Calif., said Marine Staff Sgt. Ted Martinez. Base officials were checking his background and didn't immediately know whether he was due back at the base or was to be deployed overseas.

The government does not allege that the consultant, Joseph Thomas Colon, intended to harm national security. But prosecutors said Colon's "curiosity hacks" nonetheless exposed sensitive information.

Colon, 28, an employee of BAE Systems who was assigned to the FBI field office in Springfield, Ill., said in court filings that he used the passwords and other information to bypass bureaucratic obstacles and better help the FBI install its new computer system. And he said agents in the Springfield office approved his actions.

The incident is only the latest in a long string of foul-ups, delays and embarrassments that have plagued the FBI as it tries to update its computer systems to better share tips and information. Its computer technology is frequently identified as one of the key obstacles to the bureau's attempt to sharpen its focus on intelligence and terrorism.

An FBI spokesman declined to discuss the specifics of the Colon case. But the spokesman, Paul E. Bresson, said the FBI has recently implemented a "comprehensive and proactive security program'' that includes layered access controls and threat and vulnerability assessments. Beginning last year, all FBI employees and contractors have had to undergo annual information security awareness training.

Colon pleaded guilty in March to four counts of intentionally accessing a computer while exceeding authorized access and obtaining information from any department of the United States. He could face up to 18 months in prison, according to the government's sentencing guidelines. He has lost his job with BAE Systems, and his top-secret clearance has also been revoked.

In court filings, the government also said Colon exceeded his authorized access during a stint in the Navy.

While documents in the case have not been sealed in federal court, the government and Colon entered into a confidentiality agreement, which is standard in cases involving secret or top-secret access, according to a government representative. Colon was scheduled for sentencing yesterday, but it was postponed until next week.

His attorney, Richard Winelander, declined to comment.

According to Colon's plea, he entered the system using the identity of an FBI special agent and used two computer hacking programs found on the Internet to get into one of the nation's most secret databases.

Colon used a program downloaded from the Internet to extract "hashes" -- user names, encrypted passwords and other information -- from the FBI's database. Then he used another program to "crack" the passwords by using dictionary-word comparisons, lists of common passwords and character substitutions to figure out the plain-text passwords. Both programs are widely available for free on the Internet.

What Colon did was hardly cutting edge, said Joe Stewart, a senior researcher with Chicago-based security company LURHQ Corp. "It was pretty run-of-the-mill stuff five years ago," Stewart said.

Asked if he was surprised that a secure FBI system could be entered so easily, Stewart said, "I'd like to say 'Sure,' but I'm not really. They are dealing with the same types of problems that corporations are dealing with."

Colon's lawyer said in a court filing that his client was hired to work on the FBI's "Trilogy" computer system but became frustrated over "bureaucratic" obstacles, such as obtaining written authorization from the FBI's Washington headquarters for "routine" matters such as adding a printer or moving a new computer onto the system. He said Colon used the hacked user names and passwords to bypass the authorization process and speed the work.

Colon's lawyers said FBI officials in the Springfield office approved of what he was doing, and that one agent even gave Colon his own password, enabling him to get to the encrypted database in March 2004. Because FBI employees are required to change their passwords every 90 days, Colon hacked into the system on three later occasions to update his password list.

The FBI's struggle to modernize its computer system has been a recurring headache for Mueller and has generated considerable criticism from lawmakers.

Better computer technology might have enabled agents to more closely link men who later turned out to be involved in the Sept. 11, 2001, attacks, according to intelligence reviews conducted after the terrorist strikes.

The FBI's Trilogy program cost more than $535 million but failed to produce a usable case-management system for agents because of cost overruns and technical problems, according to the Government Accountability Office.

While Trilogy led to successful hardware upgrades and thousands of new PCs for bureau workers and agents, the final phase -- a software system called the Virtual Case File -- was abandoned last year. The FBI announced in March that it would spend an additional $425 million in an attempt to finish the job. The new system would be called "Sentinel."

"Part of a comprehensive immigration plan is to give employers the tools necessary to determine whether or not the workers they're looking for are here legally in America," the US president said, flanked by immigrant workers from Iran, Guatemala and El Salvador.

"Part of a comprehensive immigration plan is to ... say to employers, 'It's against the law for you to hire somebody here illegally. We intend to find you when we catch you doing it,'" the president said.

Bush plugged his administration's "Basic Pilot" initiative, a voluntary, online verification system allowing employers to check an applicant's immigration status against federal databases. The president called for making the program mandatory.

But he also stressed the importance of making it easier for employers to legally hire foreign-born workers "for jobs Americans aren't doing."

Long-time Washington observer Stephen Hess said it was an adroit mid-course correction by the US president, whose earlier immigration reform proposals had focused mostly on measures that would normalize the status illegal workers.

"This bill was dead as a doornail -- at least through the election and into November. The president has revived it," said Hess, from the Brookings Institution think tank.

The change may have saved a immigration bill that for weeks had been hopelessly stymied, political observers said, and could also help reconcile seemingly intractable differences between House and Senate immigration bills.

The House of Representatives bill passed late last year would deport undocumented immigrants and build 1,100 kilometers (700 miles) of fence on the Mexican border.

Legislation approved this year by the Senate however, also would put key enforcment measures in place, but include channels for immigrants to gain legal status. Its provision would allow many of the estimated 11.5 million foreign workers here illegally, many of them Mexican, to gain legal status.

The rift had made adversaries of many within the Republican party, which normally prides itself on its discipline and unity.

"This could well have been a fight between Republicans and Democrats. It happened to be, interestingly enough, a fight between Republicans and Republicans," Hess said.

If the president succeeds in moving the debate forward, it can only help Republicans at the polls in November Hess said. But political analyst Thomas Mann, also from Brookings, said the maneuver also could backfire.

"Bush appears to have elevated the importance of this Novembers election over that of the long-term interests of the Republican party," said Mann, who added that a crackdown on mostly-Hispanic illegal workers could cost him with those voters.

"His shift of position may help marginally but at a steep prices with Latinos in future elections," Mann said.

Immigration reform not only was on the president's agenda, but was the topic of off-site congressional hearings Wednesday by the US House in San Diego and the US Senate in Philadelphia.

The star witness at a hearing by the Senate Judiciary Committee, New York's Republican Mayor Michael Bloomberg, lobbied strenuously for a break for illegal immigrants, who he said help prop up the city's economy.

"We need to get real about the people who are now living in this country ilegally, in many cases raising families and paying taxes," the billionaire businessman-turned-politician told lawmakers.

"The idea of deporting 11 or 12 million people -- about as many as live in the entire state of Pennsylvania -- is pure fantasy," he said.

"The economic consequences would be devastating to this country," the New York Mayor said, adding that the only practical solution is to "offer those already here the opportunity to earn permanent status and keep their families together."

"Instead of pointing figures about the past, let's accept the present for what it is, by bringing people out of the shadows," Bloomberg said.

The Long Island Rail Road car came off the tracks around 4:30 a.m. at one end of a rail yard on Manhattan's West Side. The car had not tipped over, but was positioned at an angle across several tracks, blocking trains parked inside the yard, LIRR spokesman Sam Zambuto said.

The derailment delayed trains up to 30 minutes on parts of the LIRR system, which carries an average of 274,000 people each weekday. Service on some lines was canceled while crews worked to right the train car. It wasn't immediately clear if any other commuter train services were effected.

The cause of the derailment was being investigated, Zambuto said.

The cars derailed about 5:30 p.m. Wednesday behind the Hershey American Legion post, Norfolk Southern spokesman Rudy Husband said. The post and part of the nearby Hershey Country Club golf course were also evacuated.

The 76-car train was traveling from Allentown to Baltimore, Husband said.

Last year, a train crash that punctured a tank car carrying chlorine gas in Graniteville, S.C., killed nine people and sickened more than 250 others with the toxic vapors.