Webb said he has been in New Orleans since Friday and returned Monday night. He said that he couldn't talk about the case because of the legal proceedings and his desire not to prejudice the situation. But then he denied any role in the alleged felony.
"We had three cars on Friday that were being moved about because of my trip, and that is probably a reason that this inadvertent situation developed. And that's really the extent to which I think I should be discussing. That's really all I can say," Webb told reporters.
Thompson, 45, was arraigned Tuesday in D.C. Superior Court after being arrested a day earlier for trying to enter the Russell Senate Office Building — where Webb's office is located — carrying a loaded pistol and two fully loaded magazines.
Webb's executive assistant was released on his own reconnaissance after he pleaded not guilty to charges of carrying a pistol without a license and possession of an unregistered firearm and unregistered ammunition. Thompson spent the night in a D.C. jail after U.S. Capitol Police determined Monday that he did not have a license to carry a gun in Washington, D.C., where only law enforcement officials are allowed to carry handguns.
A report filed by the arresting officer said Thompson was arrested after he placed his black briefcase on the X-ray machine. The assisting operator noticed what looked like a gun and two magazines on the X-ray screen.
"The defendant stated that he was in possession of a pistol and two magazines belonging to Senator Jim Webb. The defendant further stated that he inadvertently left the gun that he was safekeeping from the previous days," wrote Officer Elizabeth Langley. The report notes that "the weapon was test-fired and is operable."
Thompson has hired attorney Richard Gardiner to represent him. Gardiner, who said he was hired after a friend of a friend recommended him to the defendant, met Thompson for the first time earlier Tuesday. He said Thompson was "fine" but hungry.
According to court documents, Thompson celebrated his birthday in jail and away from his wife and two kids. He entered the courtroom Tuesday looking very disheveled and wearing a stone-faced expression. He was handcuffed at the legs, had no belt and one pants button was unbuttoned.
Magistrate Judge Ringelle scheduled Thompson to appear before the court on May 1 at 9 a.m. EDT for a preliminary hearing.
A senior Democratic aide said Monday evening that Thompson forgot that he had the weapon when he sent the senator's bag through the X-ray machine at the office building. The aide said Webb gave the bag that contained the gun to Thompson when Thompson drove the senator to the airport.
Thompson, a former military reporter based in Virginia, joined the senator's staff at the beginning of Webb's Senate campaign. Webb was elected to office in November. Thompson travels frequently with the senator.
Asked what support the senator was giving to his aide, Webb told FOX News, "We're doing all we can.
"I want to emphasize, first of all, that Phillip Thompson is a long-time friend. He's a fine individual. ... I have a tremendous amount of respect for him," Webb told reporters. "I think this is one of those very unfortunate situations where, completely inadvertently, he took the weapon into the Senate yesterday."
Webb also shot down rumors that he carries a gun in the Capitol complex. According to one former special assistant to the House sergeant-at-arms, lawmakers are exempt from rules that prohibit staff, visitors and others from carrying concealed weapons on Capitol grounds. Ed Bailor, a former Capitol Police investigator, said in his 32 years on the force he never heard of a senator or representative carrying a concealed weapon.
"I believe that it's important — it's important for me, personally, and for a lot of people in the situation that I'm in, to be able to defend myself and my family," Webb said. "Since 9/11 for people who are in government I think in general there has been an agreement that it's a more dangerous time. Again, I'm not going to comment, again, with great specificity about how I defend myself, but I do feel that I have that right."
Handguns are illegal in Washington, D.C., but nearby Virginia allows residents to carry concealed handguns. Capitol Police rules allow members and their employees to bring a weapon onto Capitol grounds if it is unloaded and securely wrapped. In this case, it was allegedly neither.
Webb said he is a big supporter of the constitutional right to bear arms and thinks Virginia's concealed handgun law is a "fair law."
"Everyone here knows that I am a strong supporter of the Second Amendment, that I have had a permit to carry a weapon in Virginia for a long time," he said.
Sen. Ted Stevens, R-Alaska, supports a repeal of the D.C. handgun ban. City officials are petitioning to have the case go before the full U.S. Court of Appeals for the District of Colombia after a three-judge panel of the court ruled earlier this month that the ban is unconstitutional. Stevens said the incident demonstrates "our position that we ought to have the right to bear arms, if we need to."
Stevens told FOX News that he kept a "gun in the car from time to time, before they passed that stupid law," banning handguns in the district. He said he used to keep one in his office until his staff bullied him to get rid of it. Stevens recalled that the late conservative Sen. Barry Goldwater "had a gun with him all the time ... had it with him in his car; had a holster right between his legs."
FOX News' Jim Angle, Trish Turner and FOXNews.com's Gregory Simmons contributed to this report.