A Laurel man apparently distressed over financial problems shot himself to death yesterday as he was driving east on the Capital Beltway in Prince George's County. His car then hit a tractor-trailer, snarling morning rush-hour traffic, police said.

County police said Walter Woolgar, 36, committed suicide by shooting himself in the head with a shotgun about 7:30 a.m. as his black 1977 Ford LTD passed the exits for the Baltimore-Washington Parkway.

Woolgar's car was in the far right lane when he pulled the trigger, police said. The car veered into a tractor-trailer in the next lane, Maryland state police said, and both vehicles crossed the other two eastbound lanes onto a grassy median.

The truck jackknifed on the grass, police said, and the car stopped about 100 feet away after spinning away from the truck. No one else was injured.

State police said that if the incident had occurred on the sections of the Beltway where there are no wide, grassy medians, more people and vehicles probably would have been involved.

"If either one of the vehicles had crossed into the westbound lanes," one state trooper said, "we would have had even more of a tragedy."

Woolgar, who lived in the part of Laurel that is in Howard County, was pronounced dead at the scene.

"There were cars on the left, and cars on the right," said Sgt. Mark Wright, a county police spokesman. "We were very fortunate. It could have been even more of a disaster."

Officers said a .410 shotgun was found in the front of Woolgar's car, but there was no suicide note in the car. They said they did not know why Woolgar might have chosen to kill himself while driving on the Beltway.

Robert Law, another county police spokesman, said Woolgar, who was married and the father of two children, had threatened suicide previously but had not attempted it. "Apparently, he was very depressed about financial matters," Law said.

Joyce Woolgar, 32, said in a telephone interview that her husband had been driving to his job in the parts department of East-West Lincoln Mercury in New Carrollton.

She said she was stunned by her husband's death. Although financial obligations had been piling up on the family, "we had no domestic problems," she said. "We were just in debt and having a hard time getting out."

Walter Woolgar "was diabetic and he recently had to have some surgery on his foot," Joyce Woolgar said. The accompanying medical expenses and expenses incurred for the birth of their second child Kate last March probably added to her husband's frustration, she said. The Woolgars' oldest daughter, Megan, is 4.

Joyce Woolgar, who is a receptionist at a Maryland animal hospital, said the gun used by her husband had belonged to him "since he was a child."

"I didn't realize that he even knew where it was because it was in a closet behind a lot of junk," she said.

The accident closed the eastbound lanes of I-95 near Good Luck Road for about half an hour while workers righted the tractor-trailer and county homicide investigators examined Woolgar's car.

All four eastbound lanes were opened later, police said, but traffic remained slow, apparently because of the curiosity of passing drivers, until about 10:30 a.m., when the wreckage was cleared. Staff writer Joseph E. Bouchard contributed to this report.