When a group of Reston teenagers argued with a group in Manassas about a girl last weekend, the dispute escalated far beyond bruised egos and harsh words.

Manassas police suspect that instead of separating and cooling off, the Manassas youths left a fast-food restaurant, drove 2 1/2 miles to a notoriously crime-plagued area of Dumfries, got a handgun and went back to fight. When it was over, 17-year-old Vidal Antonio Diamond, of Reston, lay unconscious. He died 12 hours later of a gunshot wound in the head. A 16-year-old youth has been charged in the case, and at least one other suspect, an adult, is sought.

The incident illustrates what law enforcement officials in Manassas and Prince William County are calling a dangerous trend in recent violent crimes: a gang-type mentality in resolving conflicts.

"We certainly don't have Los Angeles-type gangs in this area, but what we are seeing is a gang-type mentality in some of these violent crimes," said Prince William County Commonwealth's Attorney Paul B. Ebert. "It used to be that two people would get into a conflict, then go on someplace and forget about it. Now they go get a gun or some friends and come back and somebody gets seriously hurt or even killed."

For example:

David Rattliff, 17, of Alexandria, suffered severe head wounds when he was beaten with a bat and kicked repeatedly in the head Sept. 1 in a fight with five youths. Police said Rattliff and another youth argued in Woodbridge and Rattliff later returned. The other youth had gone to get friends and the bat. Keith Wester, 18, of Woodbridge, and four juveniles have been charged with malicious wounding.

On Sept. 26, Sherman Ancrum, 17, of Dumfries, was beaten and dragged into a vacant Dumfries house by two men and shot in the head. Prince William police arrested Reynaldo Radlin, 25, in Woodbridge, and charged him with malicious wounding, robbery and abduction.

Mikel Bennett, 25, of Woodbridge, died Sept. 9 of severe head injuries he suffered when he was kicked by two men. Police said Bennett was with a group of men who argued with another group. Bennett was fighting with one man when a second joined in. Paul Bellfield, 29, and Ernest Lyle, 24, both of Woodbridge, have been charged with murder, Ebert said.

"They can't let it go," said Manassas Police Chief Sam Ellis. "I spent 20 years doing police work in Fairfax before I came out here, and when a patrol officer rolled up to a fight everybody was glad to see him. Out here, police have to fight both the guys, because they don't want the fight broken up. They want to know who the ultimate winner is."

Law enforcement officials said that in the gang-like way of resolving disputes, there is a feeling that those involved would rather die than be disrespected. Gang experts said that to be disrespected or to have aspersions cast on fellow gang members is to flirt with danger.

"There's definitely a macho element involved," said Prince William prosecutor James Willett. "It's very important that face is saved."There have been more "beatings, robberies {and} assaults in the past three to four months" involving more than one attacker on a victim, said Marc Woolverton, a Manassas police spokesman.

Law enforcement officials said they can only speculate on the causes of the trend.

Willett said young people seem more willing to assist in an attack. "It's almost as if there is a territorial or clannish pride. It's not affiliated with the family group, but with friends or neighborhood. Almost like an embryonic gang situation, but not organized or structured with a hierarchy."

Willett and Ellis pointed to little parental guidance and few acceptable social activities for youths.

Woolverton said while many of the violent crimes are in the category of gang-type violence, no organized gangs have been identified.

Prince William Police Chief Charlie T. Deane said law enforcement officials are seeking stiffer penalties for those involved in group violence. He said police are now likely to arrest and charge the whole group, instead of just the instigator.

He said television and movies have created a distorted view of violence. "The young people get involved in these things, and when we investigate they tell us they never anticipated these kinds of results would occur," Deane said. "People see things in the movies and think it's romantic, but the reality's much more grim."