On Sunday night, Prince William County police were getting calls about a possible hit-and-run in a dilapidated neighborhood off Route 1 next to Quantico Marine Corps Base. Mailboxes had been knocked down, and a pickup truck was in a ditch.

When police arrived at the 18500 block of Amidon Avenue in the town of Triangle, they found the truck but no driver. They traced the vehicle to its owner, Ernest W. Bryant, 42, who, as it happened, lived one block away. Inside the tiny, cream-colored home, they found Bryant, a grocery store worker, on his living room floor. He had been shot to death.

Now, the home has been cordoned off by police as they investigate what they say is one of their more mysterious slayings, especially because it is unclear whether Bryant knew his assailant or assailants.

"It's unusual for us to get the initial call the way we did," said Charlie T. Deane, the Prince William police chief. "A vehicle was found, and no one was around. Residents thought it was a hit-and-run type of accident."

Sgt. Charlie Hoffman, the supervisor of the violent crimes unit, said investigators are looking for two people who were photographed by a surveillance camera using Bryant's ATM card in Alexandria after the killing.

"There's a bunch of photographs. Half are one guy, half are the other," Hoffman said.

The photographs show two men -- but not clear shots of their faces -- who are wearing black ski caps. One has on what appears to be a denim jacket; the other is clad in a flannel, short-sleeve button-down shirt. They are seen separately walking into an alcove with an ATM and using the card and leaving.

Paul B. Ebert, the Prince William Commonwealth's Attorney, sketched out one of two possible scenarios.

"He died of a single gunshot wound . . . and it appears the victim either knew the assailant and allowed him into his home, or the suspect was an intruder and [Bryant] was unaware of his presence," he said.

Ebert said that if the suspect or suspects are caught, he will consider pursuing a death penalty case because the motive for the killing might have been robbery.

Maj. Ray Colgan, assistant chief for criminal investigations for the police department, said that detectives are pursuing several leads but that the case is complicated by the fact that Bryant, who was single, lived alone.

"I can't recall that we have had a murder down there in awhile," Colgan said. "We've got 15 detectives going in 15 different directions."

Police are waiting for the autopsy to be completed.

Bryant had worked at Food Lion in Stafford County for several years, according to Jeff Lowrance, a company spokesman. "Fellow employees are shaken up today and are, of course, sad," he said in a voice mail message, but he declined to allow a reporter to interview them.

Many residents in Bryant's neighborhood did not know the victim or were not home yesterday afternoon. His home was surrounded by yellow police tape and guarded by a police officer in his cruiser with the engine running.

Ron Emmons, owner of a dental laboratory a few houses down from Bryant's, said he did not know the victim, but he said it was jarring to learn that a slaying occurred so close to his business.

"Never, ever had nothing like that," he said. "I can't believe somebody got murdered."

Prince William County police keep watch over the Triangle house where grocery worker Ernest W. Bryant, 42, was found dead. Investigators are looking for two men photographed by a surveillance camera in Alexandria using the victim's ATM card.