A man who moved his jewelry store to the Aspen Hill Shopping Center, seeking better security than he had in a former location, was fatally wounded yesterday when he traded gunshots with a holdup man in his store, Montgomery County police reported.

The holdup man drove from the scene, chased by an off-duty Washington fireman, police said, then managed to evade capture by 100 police searchers for about 3 1/2 hours. Finally police took into custody a suspect they found sitting in a red MG sports car in the driveway of a home about two miles from the shooting.

The suspect, whom police were questioning last night, gave his age as 31, but police said he refused to give his name or address. An effort was being made to identify him through his fingerprints.

Police said the shooting occurred about 11 a.m. when Alvin Insley, 52, returned to his store, Insley Jewelers, after getting a cup of coffee at a nearby High's Dairy store.

A store employee said a man had come in and asked to see a ring, then drew a gun, handcuffed her and told her to lie down in the back of the store.

When Insley entered, he pulled out a handgun and fired at the holdup man, who fired back, wounding Insley in the leg, stomach and arm, according to police.

As the gunman fled in a red Datsun, witnesses said, Insley collapsed in front of a display window filled with diamond wedding rings. "He just said, 'help me,' nothing else," recalled Albert Harris, owner of the Aspen Hill Optical Co., who ran out of his store when he heard shots and glass breaking.

Insley died about 1:30 p.m. at Montgomery General Hospital.

The off-duty fireman, whom police did not identify, chased the Datsun from the shopping center and was shot at during his pursuit, according to Pfc. Rick Nelson, a county police spokesman.The Datsun - which police said had been stolen - was abandoned on a deadend street behind the Holiday Park Elementary School, Nelson said, and a search involving helicopters and county, state and U.S. Park Police ensued.

The suspect was arrested about 2:30 p.m. in an MG that was parked in the driveway of a home in the 4000 block of Adams Drive, police said.

Relatives of Insley said he had been a jeweler for more than 25 years. His first store, in Langley Park, had been robbed about three times, according to Janet Insley, his daughter-in-law. She said Insley moved to the Aspen Hill center, an area flanked by Wheaton, Silver Spring and Kensington, seeking better security.