ARLINGTON, Va. — It has been four months since Paul Zeller, 24, was gunned down within walking distance of the Pentagon, and there is no suspect in sight. He had survived a hard year as a soldier in Iraq only to die in a clean, well-lighted place in suburban America.

Frustrated by the lack of progress in the investigation, relatives and friends have passed out hundreds of fliers and offered a reward of more than $3,000 to pry out information that might lead to an arrest.

Each time they return with a new stack of fliers to the busy stretch of malls and high-rise apartments that Zeller passed moments before he was slain June 30, they wonder how the crime has remained unsolved for so long.

"It's so close to where such a large number of people live," said Navy Cmdr. Lydia Robertson, Zeller's sister, who lives less than a mile from the scene. "I'm disappointed that there hasn't been more of a response from people in that area. Maybe they were in bed, but with all the high-rises overhead, someone had to hear and see something."

For Arlington, a prosperous Washington, D.C., suburb overrun each day by thousands of military personnel and government workers, Zeller's slaying was more than just a cruel irony visited on a safely returned soldier and his family.

The Department of Defense does not keep figures on the number of Iraq veterans victimized by violent crime around the nation. But in Arlington, where homicides rarely surpass four or five a year, Zeller's death also remains unusual because of its setting and the weapon used to kill him.

Arlington police spokesman John Lisle would not comment on the type of weapon used, but those familiar with the case said Zeller was slain at close range with a shotgun, a weapon that Lisle confirmed rarely had been used in recent slayings and shootings investigated by the department. There is no clear evidence of a robbery, Lisle said, and police don't know whether Zeller was targeted or a random victim.

Although it was just after midnight, "there were a lot of people in the vicinity and close by when it happened," Lisle said.

Witnesses described a deafening blast. Zeller's body was discovered at 12:06 a.m. near a market. He suffered multiple wounds to his upper body.

"We're pretty confident we've talked to everyone who was willing to share information," Lisle said. "We're hoping now we can draw out people who have any information they may be reluctant to share because they're nervous or they think it's insignificant."

Zeller joined the Army after the Sept. 11 attacks and went to Iraq with the 82nd Airborne Division as an artilleryman assigned to a mortar unit. He was discharged in September 2004 and moved in with Robertson and her husband, a Marine who has also served in Iraq.