When Prescott Sigmund arrived in this working-class college town nestled in the Rocky Mountains in July, he quickly slipped into a lifestyle very different from the one he had known in suburban Washington.

Throughout the summer, he rose about 5 a.m. to pedal a bicycle five miles to the motel where he worked as a desk clerk. He lived in a ranch-style house with three other men and the landlady, who agreed to cut his rent in exchange for housecleaning chores and snow shoveling during the winter.

When acquaintances noticed that he sometimes looked depressed, he told them it was because his wife and children had been killed in a crash with a drunk driver.

Sigmund told friends he liked Missoula and planned on staying here. That all changed on Saturday night, when saw his own image broadcast on Fox television's "America's Most Wanted" as the fugitive charged in a July 12 pipe bomb explosion in the District. Shortly after the program aired, he surrendered at the Missoula police station.

Sigmund, 35, who had vanished three days after the explosion, is to appear before a federal magistrate here Tuesday, said Channing Phillips, a spokesman for the U.S. attorney's office in the District. He faces an extradition and detention hearing, which he could choose to waive. Phillips said it is likely that Sigmund will return to Washington later this week or next week.

The two pipe bombs critically injured Sigmund's half-brother, 21-year-old Wright Sigmund. Authorities allege that the intended target was their father, insurance executive Donald Sigmund, who owned the Chevrolet Blazer where the bombs went off. Wright Sigmund had borrowed the vehicle that day.

Before his disappearance, Prescott Sigmund had lived with his wife and two young sons in the affluent River Falls section of Potomac and in recent years had sold insurance and human resources products.

But he told people in Missoula, who knew him as Paul Nott, that he had been working in maintenance and construction in southern Virginia and decided to leave his job after his boss retired. His Montana co-workers and friends said that no one suspected otherwise.

"He fit into Missoula because he was laid-back and easygoing," said one acquaintance, who agreed to be interviewed on the condition that he not be identified.

Sigmund apparently arrived here by bus not long after fleeing the Washington area. His first night in town, he stopped by the local shelter for the homeless but opted to camp out instead. Missoula has its share of hobo camps in the summertime along the Clark Fork River, and Sigmund, carrying his possessions in a backpack, wouldn't have had to hike too far upriver to find a secluded camping spot.

Within a week, he rented a room for about $250 a month in a single-story home in a quiet residential area, about a block away from Missoula Sentinel High School. The three other renters, also male, either worked at or attended the University of Montana. He began working as a desk clerk at the Comfort Inn in July, according to Melanie Hatter, a spokeswoman for Choice Hotels in Silver Spring, the inn's parent company. She said she did not know what day he started his job.

Sigmund rode his bicycle or walked to work until the fall, when he purchased a 1970s model Mercury.

Sigmund, who took to wearing a Florida State ball cap, quickly settled into the unpretentious Missoula lifestyle. Co-workers gave him a used television set and a computer, for which he bought a desk at Wal-Mart. About his only other possessions were his clothes and his backpack, friends said.

He seemed to charm people he met and sometimes went out of his way to cement friendships within his small circle of acquaintances and co-workers -- helping a co-worker's husband build a shed, driving roommates to the laundromat or mall, babysitting on weekends for co-workers.

Friends said Sigmund liked going for Saturday morning breakfasts or dinners at the Golden Corral Buffet. Occasionally, he attended a football game of the University of Montana Grizzlies, the number one Division 1-AA team in the nation, and went to bars along the town's retail and restaurant strip to watch pro games on Monday nights.

When he walked into the Missoula police department to give himself up, the normally cleanshaven Sigmund was sporting a beard and had no identification, said Sgt. Travis Welsh. Welsh said officers were able to identify him by calling up the Web site of "America's Most Wanted," where Sigmund's photo was displayed.

Sigmund is being held on a federal charge of transportation of an explosive device with the intent to harm someone. Law enforcement sources said today that investigators found a wire at Sigmund's home in Potomac that had been cut in the same fashion as a wire attached to the pipe bombs. Sources previously had said that wooden matches used in the bombing were linked to Sigmund.

Wright Sigmund's mother, Claire Stanard Phillips, said she spoke to Donald Sigmund today about the arrest.

"I think his reaction is the same as everybody, just relieved that there's some closure," she said. "He has felt a sense of relief -- sadness, but relief."

She also said she had told authorities all along that Sigmund had probably gone to Montana or Wyoming because he liked cold weather and loved to fly fish.

Staff writer Allan Lengel contributed to this report.