A burglary suspect who was shot and killed by Prince George's County policeman Lester J. Bethel early Saturday died of shotgun pellet wounds in the back and in the front left shoulder, an autopsy revealed yesterday.

Deputy State Medical Examiner Dr. Bert Morton said the autopsy of Abraham Dickens IV, an 18-year-old Palmer Park man, did not determine which of the two shots struck the victim first.

Dickens was shot at 5:30 Saturday morning as he was climbing out the rear window of the Palmer Lounge, a restaurant and liquor store on George Palmer Highway, according to police reports. The reports said Dickens had just burglarized the establishment when he was confronted by Officer Bethel.

Bethel told homicide investigators that he then ordered Dickens to freeze. "At that time," the police report said, "the suspect made a movement with his right arm. The officer fired one shot from his shotgun, then dropped to the ground and fired a second shot. The suspect fell back inside the building."

Bethel, who has been placed on administrative leave pending an internal investigation of the shooting, has refused to comment on the incident. Police investigators declined to elaborate on the officer's explanation that he fired because he saw Dickens "move his right arm."

The Dickens shooting marked the third time in the last three years that Bethel, 26, who joined the county police department in 1972, has used his firearms to apprehend a suspect. Although Bethel was cleared by the department's internal affairs division in both previous instances, civil suit stemming from one of them is still pending against him.

The suit involves an incident that took place on August 29, 1976. Late that night, according to polce reports, Bethel was driving his patrol cruiser along Southern Avenue when he saw a man with a knife chasing another man down the street.

The police account said Bethel left his cruiser and ordered the man, 19-year-old James Edward McPhaul, to halt. Then, according to police, McPhaul turned toward the officer and, when ordered to drop the knife, instead moved toward Bethel. Police said Bethel then fired one shot at McPhaul, wounding him in the stomach.

Since the shooting took place just across the county line in Washington, it was investigated by the Washington police force and U.S. Attorney's office in the district. A federal grand jury examined the case, but chose to indict neither Bethel nor this alleged assailant, McPhaul.

Attorney Selma Samols, representing McPhaul in the civil suit against Bethel, offered an entirely different account of the incident.

"My client, a kid, was playing a running game of tag with four of his friends that night." said Samols. "My client had a pocket knife in his hand, which was closed when he was chasing one of his friends.Bethel saw and yelled at him to come toward the police cruiser. We claim that Bethel never got out of his cruiser. He sat there and shot McPhaul as he was approaching the car. Lester Bethel should not be allowed to carry a gun."

Bethel's attorney in the civil suit is Deputy County Attorney Michael Connaughton. "I'd not like to comment on it right now," Connaughton said yesterday. "It's a case under litigation and it doesn't help anyone to talk about it."

Samols said she expects the case to be settled out of court. "They (the county) may pay his medical expenses of $5,000," she said.

In 1975, according to county police reports, Bethel shot a 17-year-old Calvert County youth in the neck after chasing him down during a high-speed auto chase in Upper Marlboro. In that case, police said, Bethel's gun discharged accidentally during a struggle with the youth.

The youth, who was charged with assaulting a police officer and resisting arrest, claimed that Bethel shot him after he had surrendered. The internal affairs division exonerated Bethel in that case, saying he acted properly under the circumstances.

Police investigators said that when Bethel shot Dickens Saturday morning there were two other officers on the scene, both on the side of the restaurant. In addition, a man and a woman who were lodged in two apartments located above the restaurant, claimed to be "ear witnesses" to the shooting.

Carol Brewer, who works as a bar-tender at the restaurant, said she was staying overnight in one of that apartments because she could not drive home during the snowstorm Friday night.

"I was upstairs when the alarm went off," said Brewer. "I jumped up and ran down the steps and looked out the front door, but didn't see anything. I ran back upstairs and called the police. They were here within two minutes."

Brewer said she remembered seeing "eight or 10" policemen around the building at the time of the shooting.