The deaths of a Woodbridge couple found shot on a lonely stretch of road near London Reformatory on Tuesday night have been ruled a murder and suicide, Fairfax County police said yesterday.

They said that Douglas D. Canody, 38, shot his wife Peggy, 39, once in the upper chest and then shot himself in the right side of the head with a 30-caliber rifle.

The Canodys, who had four children ages 18, 14, 10 and 8, had argued before driving away from their home at 1603 Georgia Ct. police said.

Canody was an operating engineer at a downtown office building and his wife was a secretary for the Navy Department at the Pentagon.

A police spokesman said a motorist driving along Ox Road, Rte. 123, about a quarter mile from the Prince William County line, stopped his car at about 8:30 p.m. when he saw a woman running down the road shouting that her husband was trying to kill her.

The motorist who identified himself as Robert Hopkins, said the woman cried out "Help me! Help me!" grabbed the driver's door to his car and said, "My husband's going to shoot me."

Hopkins, an insurance salesman from Fairfax Station, said a man with a rifle cradled in his arm then walked from a nearby pickup truck toward his car and said, "That's okay, buddy, you keep moving."

"He started to point the gun at me," said Hopkins, who said he crouched down on the passenger side, hit the gas pedal with his foot and pulled away.

Hopkins said he had driven about 400 yards when he heard two shots. He said he then searched in vain for a telephone at a nearby water treatment plant before driving to Lorton Reformatory where officials called police.

"It's a very helpless feeling. There's nothing you can do," Hopkins, 41, said.

Police rushed to the scene but found both dead. Peggy Canody, dressed in slacks and a white pullover sweater, was lying on her back in the middle of the northbound lane. Her husband, wearing work clothes, was lying face down about 10 feet away with the rifle under his body.

James Haynes, a neighbor of the Canodys, said the family had lived next to him for about 15 years. "Everybody has some problems but this is something that shouldn't have happened," he said.

Haynes said the Canody children are "just like my own children."

"The older two understand pretty good, but it hasn't hit the younger two yet," Haynes said. "I'm going to try to protect them as best I can."