It was after midnight one morning when two gunmen with semiautomatic weapons burst into an auto repair shop in Northeast Washington and sprayed it with bullets, wounding one man and killing another.

As the gunmen fled down 14th Street, an off-duty D.C. Police officer -- filling his car with gas at a station nearby -- ordered them to stop. They turned and fired toward the officer, Clarence D. Douglas, who returned fire with his police handgun.

"The bullet hit the man's jacket, and ripples went through the clothing," recalled D.C. firearms instructor Larry Melton. "But the guy wouldn't go down. The officer knew he was hitting him because he told me that he saw the clothing waft. Then it dawned on him. The guy was wearing a bulletproof vest."

What Douglas saw that morning in April 1989 signaled a new trend in drug traffic areas in the District and Prince George's County, police say. Bulletproof vests -- worn by thousands of officers across the country in recent years -- are becoming standard issue uniform for drug dealers.

"We're definitely seeing more vests on the streets, and it's a real problem for officers," said D.C. Police Chief Isaac Fulwood Jr. "There is growing concern in the law enforcement community."

Hubert Williams, president of the Washington-based Police Foundation, a nonprofit research group on police issues, said the vest phenomenon is a result of the violence borne of illegal drugs. "Criminals have every piece of technology we have in law enforcement, and some we don't have," Williams said. "They know it's violent out there, and they're taking every step they can to increase {their} edge."

The proliferation of vests -- or "soft body armor," as police call it -- is forcing police instructors like Melton to change firearms training for recruits, who are taught to shoot in life-threatening situations.

"We've started teaching the officers that if they are within 10 feet to shoot into the center of mass," Melton said. "But if nothing happens, and the guy is still standing and not going down, then he apparently has a vest on. We teach them to then go to the head quickly."

In the past year, the Drug Enforcement Administration also has changed its firearms drills for agents at the Quantico training center and in field offices nationwide, said DEA spokesman Bill Ruzzamenti. "We went into these different drills of two shots to center mass and one to the head, because our intelligence information is that some bad guys are wearing bulletproof vests," he said.

Police say it's rare for law-abiding citizens to wear the vests, but common for drug dealers who need them to do business in a dangerous trade. "They aren't dumb," said Assistant Police Chief Melvin High, head of field operations. "The danger is increasing."

Other combatants in the local drug war are also wearing vests. Some D.C. ambulance workers have spent $300 to $500 for their own vests to protect themselves when they arrive early at a crime scene and the bullets are still flying.

District and Prince George's officials don't have statistics on dealers' use of vests because officers seize the garments only if they're worn by individuals arrested. But anecdotal data supports the assertion of one detective from the 7th police district in Southeast that "the players all have vests."

One narcotics officer told of a 13-year-old, suspected of selling drugs, who was wearing a bulletproof vest on H Street NE. In January, at the murder scene of a teenager gunned down on the corner of 16th and Isherwood Streets NE, a detective interviewing a crowd of youths expressed surprise that many were wearing vests, visible under sweatshirts or detectable during a patdown.

In February, when police stopped a pickup truck in Southeast, they found the leader of an alleged drug group that investigators say is involved in a deadly feud with a rival gang. Officers arrested the leader, Eddie Jerome Mathis, and three other people inside on weapons charges. All four were wearing vests, three of them heavier military flak jackets. Officers believe the four were anticipating battle.

In Prince George's County the same month, two gunmen burst into Players Billiards Parlor, which is in a drug area, and sprayed it with semiautomatic weapon fire. The intended victim, wearing a bulletproof vest, escaped unharmed . Two bystanders were killed.

Early yesterday, a gunman fired in a crowded nightclub in Langley Park, wounding three people. Two of them were wearing bulletproof vests.

Last year, U.S. Park Police chased a stolen sports car on the Baltimore-Washington Parkway through Cheverly at speeds up to 80 miles an hour, until the car crashed. One of the two 17-year-olds inside was wearing a bulletproof vest.

The vests are not illegal, and can be bought from catalogues, and from local gun shops, military surplus stores and security companies.

Some company owners and gun store managers said they sell vests only to law enforcement officers. "I'm very cautious," said Bruce Anderson, manager of the Old Town Armory in Alexandria. "Everyone here is instructed to only sell to police officers or someone who proved to me that they had a need for a bulletproof vest."

Others in the industry also are practicing caution. Manufacturers imprint serial numbers on vests to track them the way guns are.

But criminals still manage to get vests the same way they do weapons -- surreptitiously, and on the underground market. "Of course these people are wearing flak jackets," said Mario Perez, the DEA Washington field office's spokesman. "You see Uzis, Mac 10s and submachine guns out there."