The first clue that the day would be different came when neighbors saw men in suits snooping around the slate-colored duplex.

"They just moseyed up and started looking around like they owned the place," said Dean Resop, who lives a block away from the home.

The strangers were FBI agents. Within hours, it became apparent that the working-class community had become the latest focus of the investigation into the Washington D.C.-area sniper shootings that have left 10 people dead and three others critically wounded since Oct. 2.

The FBI refused to say what it was looking for at the property on South Proctor Avenue. But law enforcement sources speaking on condition of anonymity confirmed the agents were seeking evidence at the rental home related to ammunition.

Also Wednesday, FBI agents visited Bellingham High School, 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 on an older man. He said both left the area about nine months ago.

Chris Waters, an Army private at Fort Lewis, lives directly across from the duplex. He said he heard repeated gunfire from somewhere in the neighborhood almost every day in January, but he wasn't exactly sure where.

"It sounded like a high velocity round," said Waters, who fires a variety of high-powered weapons as a soldier.

Eventually, Waters said, he called police and they cruised through the neighborhood. He said they didn't find anything suspicious.

"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."

While children played in the late afternoon sunshine Wednesday, their parents watched investigators cut up and remove a tree stump, pull up nails and examine a 55-gallon burn barrel.

"They cut the burn barrel in half. They went through that for a good hour," said Matt Cousineau, who lives next door to the duplex. "They are not missing a square inch of that yard."

Shelly Eberwein, who lives on the other side of the Cousineau duplex, said investigators were digging up part of the yard when metal detectors went off.

She said agents reassured her there was no danger but also refused to elaborate on what they were doing.

The neighborhood of mostly single-family homes is neat but sparsely landscaped. The duplex appeared to be of late 1960s vintage, with a burned-out car in the carport.