Raymond Hubbard, the 28-year-old Prince George's policeman who was slain in Iverson Mall Monday as he tried to stop a jewelry store robbery, was described yesterday as a levelheaded, easygoing officer who was looking forward to getting married soon.

Off duty at the time, he had just left his Silver Hill apartment and entered the Hillcrest Heights mall a quarter-mile away to buy a present for his girlfriend.

Hubbard may have been thinking about his wedding plans. Or perhaps it was the trip for two to Puerto Rico set for March, the only thing he had ever won in his life.

"He just happened to tell a couple of people he was going by to get me a present," said Loretta Allison of Temple Hills, his steady for more than a year, whose birthday is this Friday.

Then he heard a robbery was taking place. It was his beat, and the two-year veteran responded.

"He was a very levelheaded individual. He would not walk into something foolishly," said Officer Michael Porter, his best friend on the force. "He was as much taken by surprise as those guys were," Porter said.

When Hubbard ordered one of the three masked gunmen running past him from Kay Jewelers to halt, a second gunman opened up from behind, police said. Then the first gunman began firing from the front. Hubbard never had a chance.

"We believe that he may have gotten off some shots, but he was fired on from two points," police spokesman Art DiGennero said.

"From all indications there were probably 15 to 20 shots fired,"spokesman Robert Law said.

The shots scattered panicked shoppers to shelter in half a dozen stores, and many of the shoppers called the police. Two bystanders were hit. A bullet passed through the legs of a shoe store manager, and another grazed the wrist of a shopper, according to spokesmen from Prince George's General Hospital.

Hubbard was pronounced dead at that hospital at 7:22 p.m. Prince George's police have called on all area jurisdictions in the search for the three suspects, whom they describe as being 18- to 21-year-old men.

Police yesterday questioned a man who was dropped off at the Howard University Hospital emergency room Monday night suffering from a gunshot wound in the back. Police said the man, admitted to the hospital in serious condition, is 21 years old and completing a sentence for armed robbery by residing at a halfway house in Washington.

Police said he first told them he had been shot during a fight but was unable to say who brought him to the hospital or where the fight occurred. Yesterday, police said, the man told them he had been wounded by a stray bullet fired during the Iverson Mall incident.

A 1974 Pontiac commandeered by one of the suspects as he fled the scene of the shooting Monday night was found yesterday in Southeast Washington. Police were still looking for a brown and white 1977 Buick with Maryland license plates that was stolen by the second gunman as he made his escape.

The 866 officers of the county police force are wearing black ribbons over their badges for only the 12th time in their 51-year history. County flags were at half mast in yesterday's drizzle.

Hubbard was one of several black officers recruited from neighboring areas--so aggressively that Alexandria officials complained a few years ago as Prince George's moved to increase the number of blacks on its once all-white police force.

Before Hubbard, the last Prince George's officer killed in the line of duty was Antonio Kelsey; he was slain Feb. 3, 1980.

Born in Warner Robins, Ga., Hubbard came to the Washington area after serving in the Air Force. He had also worked as a fingerprint technician for the FBI before joining the Alexandria Police Department. According to friends, he was not there for more than a year before he moved to the better-paying Prince George's department in April of 1980.

Hubbard worked out of the Oxon Hill station, covering the relatively high crime sector bordering the District of Columbia in the Hillcrest Heights area.

"He was very easygoing and quiet. He approached his work in a diligent manner," said Lt. Wallace Andrzejewski, Hubbard's commanding officer at Oxon Hill. Andrzejewski said his men are "very numb about [the slaying] now. I'm sure they'll be a bit apprehensive when they answer anything from now on."

About 100 officers attended a memorial service last night at the Fraternal Order of police lodge in Largo. Funeral arrangements are awaiting the arrival of Hubbard's mother, Lillian Haynes, from Georgia.