ROCKVILLE, Md. – The Beltway Sniper's three-week murder spree may be over.
Police swooped down and arrested a man and his stepson at a Maryland rest stop Thursday morning in what officials say is a major break in the case.
Members of the sniper task force arrested John Allen Muhammad, 41, and John Lee Malvo, 17, at 3:19 a.m., just a few hours after a warrant had been issued for their arrest.
The pair were found sleeping inside a 1990 blue Chevrolet Caprice off I-70 in Frederick County, Md.
Police reportedly found a gun, a scope and a tripod in the car, and a law enforcement source said the gun appeared to have the same caliber as the one used in the shootings of 13 people, 10 of whom died. Police were awaiting ballistics tests on the gun.
Muhammad was being held on a federal gun violation; Malvo was being held as a material witness, law enforcement sources told Fox News.
Montgomery County state's attorney Douglas Gansler said he believed the sniper was no longer at large.
"There's a strong feeling these people are related to the sniper shootings," he said.
Another official, who requested not to be identified, said of Muhammad and Malvo: "We're positive it's these guys."
The pair were transported to Montgomery County, Md., where the investigation is based. Their car, bearing New Jersey license plates, was also brought to a police facility in Gaithersburg, Md.
Asleep at the Wheel
A motorist and an attendant at the Frederick County rest stop called police at 1 a.m. after they spotted the pair sleeping inside one of the cars sought in the sniper investigation.
Police responded and took the pair into custody.
Sources told Fox News that they had received an earlier tip on Muhammad from a friend of his who said Muhammad had described one of the shootings with details only the shooter could have known.
Police issued an arrest warrant for Muhammad Wednesday night, saying they believed he had information about the string of terrifying shootings that have left 10 people dead and three others wounded since Oct. 2. They issued an alert for the Caprice and a white 1989 Chevrolet Celebrity with Maryland plates.
Montgomery County Police Chief Charles Moose cautioned that the public should not assume Muhammad is involved in any of the shootings that have stricken the Washington area.
Moose identified Muhammad as a 6-foot-1, 180-pound black male who also goes by the name John Allen Williams, and authorities released a photograph showing a clean-shaven man with closely cropped hair.
Moose also issued another direct message to the sniper Wednesday night: "Let's talk directly. We have an answer for you about your option. We are waiting for you to contact us."
"You asked us to say 'We have caught the sniper like a duck in a noose.' We understand that hearing us say that is important to you," Moose said. "Let's talk directly. We have an answer for you about your option. We are waiting for you to contact us."
The sniper reportedly demanded $10 million in a message to authorities.
Muhammad's ex-wife, Mildred, was questioned by the FBI Wednesday, said Adele Moses, who identified herself as the woman's sister. She said Mildred was living with her in Clinton, Md., southeast of Washington.
Links in Washington State
The Pierce County, Wash., sheriff's office said Muhammad was once stationed at Fort Lewis — an Army post south of Tacoma that provides some of the most intense sniper training in the military — and had also been based at Fort Ord in California. He also reportedly served in the Gulf War.
Muhammad served in the Army as a machinist and had no training as a sniper, according to a senior defense official. Another official said Muhammad was discharged from the Army in the mid-1990s.
In Tacoma Wednesday night, FBI agents spent hours at a rental home, eventually carting away a tree stump from the yard and other potential evidence in a U-Haul truck. The back yard was divided into grids by tape and agents swept metal detectors back and forth in a painstaking search.
The stump was en route to the agency's lab in Rockville, Md., for ballistics testing. Law enforcement sources said they believed the stump might contain bullets or fragments.
Pfc. Chris Waters, a Fort Lewis soldier who lives across the street from the home, said he called police after hearing gunshots in the neighborhood nearly every day in January.
"It sounded like a high-powered rifle such as an M-16," he said. "Never more than three shots at a time. Pow. Pow. Pow."
FBI agents also visited Bellingham High School Wednesday, 90 miles north of Seattle. Mayor Mark Asmundson told the Bellingham Herald the agents were apparently seeking information on a male teenager who once attended the school and an older man. He said both left the area about nine months ago.
Bellingham, Wash., Police Chief Randy Carroll said Malvo, who authorities said is a citizen of Jamaica, briefly attended high school in Bellingham "and then moved on."
Investigation Extends Into Alabama
At a Thursday morning press conference, Montgomery, Ala., Police Chief John Wilson commented on reported links between the sniper and a Sept. 21 liquor store robbery in Montgomery. Claudine Parker, 52, was shot and killed in the robbery and another woman was wounded as the two walked to their cars after locking up the store.
Wilson said there was no "absolute" link between the robbery and the sniper, but acknowledged that a composite drawing of the suspect in his case bears a resemblance to a photograph of one of the two arrested in the sniper case. He said the gun used in the sniper shootings was not the gun used in Montgomery.
Wilson also denied reports that a credit card and note were found at the liquor store.
Montgomery Mayor Bobby Bright said a caller to the sniper investigation tip line apparently claimed responsibility for the sniper shootings and the Montgomery shooting.
A law enforcement source told The Baltimore Sun that police found a piece of paper at the scene of the Montgomery shooting that bore Malvo's fingerprints. Police then traced Malvo to a Tacoma house where he had been living with Muhammad, the paper said. Wilson would not confirm this information.
Terror Ties Probed
Several federal sources told the Seattle Times that Muhammad and Malvo may have been motivated by anti-American sentiments in the wake of the Sept. 11 attacks. Both were known to speak sympathetically about the men who hijacked jetliners over Washington, New York and Pennsylvania, the sources said.
But Police Chief Carroll said Thursday morning that Muhammad and Malvo "were not acting with any group or with any organized group of people. It appears that they have acted on their own."
The FBI also searched a location near Marion, Ala., known as Camp Ground Zero USA — a training camp for U.S. law enforcement and security experts from other countries, a facility source told Fox News.
FBI sources later said Ground Zero USA has nothing to do with the current sniper investigation.
Fox News' Brian Wilson, Rita Cosby, Ian Christopher McCaleb, Jonathan Serrie, Andrew Hard and the Associated Press contributed to this report.