CRISIS IN THE CARIBBEAN : Threats of Vengeance Simmer Beneath Thin Veneer of Order : Violence: Mob attack on police officer, rising price of weapons are among signs of potential for chaos.

As hundreds of Haitians gathered to grin, cheer and wave the leafy branches that are a symbol here of rebirth, Army Staff Sgt. Richard Hahn knelt Sunday in a soccer field just outside the center of the capital and breathed a sigh of relief.

The first street patrol of his 10th Mountain Division’s Bravo Company--part of a show of U.S. force in the air and on the streets in the aftermath of Saturday night’s shootout in the northern port town of Cap Haitien--had come off without a hitch.

“When I got the word last night about what happened up in Cap Haitien, I thought: ‘Whoo, here we go again. This could get bad,’ ” Hahn said, referring to the Saturday night incident in which 10 Haitians identified by U.S. officials as police were killed by Marines in a town where Haitian security forces then collapsed.

Hahn, who served in the U.S. intervention in Somalia, said he and his company had learned a critical lesson in their 4 1/2-month tour in the anarchy and destruction of Mogadishu, the urban nightmare where America’s last military adventure abroad turned against it almost overnight.

“I’m glad all these people are friendly,” he said. “But we’re always conscious of the crowd around us now. And we always expect it could change any moment.”

All around him, this city was showing the seeds of change. And the scenes that played out in several neighborhoods Sunday underscored just how fragile the U.S. military toehold is here and how thin is the veneer of order in a capital where chaos could be just another firefight away:

* In the city’s worst slum, Cite Soleil, there was another slaying overnight. A 40-year-old stove maker and father of 20 was found dead in the mud with gunshot wounds. As dozens of relatives grieved, no police showed up to investigate. A local radio station reported that the dead man had taken part in Saturday’s pro-Aristide demonstration.

* In the markets, the price of weapons jumped Sunday. Fueled by increased demand and shrinking supply, an Israeli-made Galil was $2,500, an Uzi submachine gun, $1,500, and grenades were $100.

* Just two miles from where Bravo Company patrolled, thousands of residents of the Carrefour slum were celebrating their attack on Thelus Jean Erby, a Haitian police officer, the night before. Their only regret: He was still alive. The mob had surrounded his small neighborhood police post and chased him through the mud, straw and cinder-block huts of their slum until he threw himself into a cesspool to escape their wrath.

It took three hours for several dozen police and firefighters to rescue Erby, who was taken to the Military Hospital, where doctors said he was recovering from trauma Sunday.

In interviews with several residents, it was clear that Erby is lucky to be alive.

“Of course, we would have killed him, if we caught him,” said the shirtless proprietor of a tiny grocery shack. “He’s a bad man. He has killed people here and extorted money from us for a long time. It is time now that he gets what he is due.”

The Carrefour residents said their fury bubbled over after three years of repression. They also were clearly emboldened by the U.S. military presence here. The U.S. troops now have permission to use force, if necessary, to check brutality by Haiti’s police and army in the weeks before the junta steps down, by Oct. 15.

“This policeman tried to set fire to my house, even as he fled,” asserted Fifi Roche, explaining that Erby broke down the wall of her shack when he tried to hide there from the mob at one point. “I would have chased him too, but I was afraid for my seven children. He had a machete and threatened us.”

“It’s a shame he got away,” added one of her neighbors. “He should be dead, along with the other so-called ‘policemen.’ ”

Down the hill from that slum, in Haiti’s colonial-style military headquarters downtown, there was a different spin on the day’s events. The lieutenants, sergeants and corporals there reacted with outrage and fear to the increasingly real prospect that they may be subjected to popular revenge.

As the tide of power turns so quickly against them with the arrival of U.S. troops--whose principal mission is to reinstate the exiled president whom many of those officers helped overthrow in 1991--the Haitian military personnel stressed that the threat of anarchy is inseparable now from that of vengeance.

“Destroy us, and you destroy the last institution still standing here,” one low-ranking officer said in perfect English. “What you saw with this one policeman who was chased into the open sewers is just the beginning. I just don’t think the Americans know what they’re dealing with here right now.”

Neither did Romuald Jean, deputy news editor of what is left of Haiti’s national state-run television station. He sat drinking a beer Sunday morning in an otherwise abandoned newsroom and said that he too believes that the mob chase was a foreshadowing of bloodletting to come.

“Yes, yes, yes, there will be a lot of revenge now,” he said with a knowing stoicism. “People are afraid, yes--the people who have reason to fear and even some who don’t. When the Haitian police are gone, when the army is gone, only the American troops will be left. And what will happen then? I don’t know, and maybe they don’t either.”

It’s unlikely that viewers will get their news from Jean’s Haitian Television Network, something of a symbol of the nation’s many faded institutions.

Unlike many military regimes, the Haitian junta has stationed no guards around this country’s only television station, which rarely is on the air. It usually broadcasts only soccer matches, and Jean said he is unsure just when his next newscast will be.

“It doesn’t really matter,” another station employee said. “Nobody watches it anyway anymore.”