The gang violence that claimed the lives of a 12-year-old girl and a 15-year-old boy last week has sparked public outcry and intensified police patrols on the streets.

Jolesa Barber, 12

Despite the killings, gang violence is not on the rise in Pittsburgh, according to city police. But as police mounted the stepped-up offensive, they faced what many experts say is a daunting job -- quelling the small, dispersed gangs that plague many city neighborhoods.

On Monday, Jolesa Barber was killed when her sister's Perry South rowhouse was sprayed with more than 40 rounds from an AK-47 in a shooting that police said stemmed from a feud between two neighborhood gangs.

The following night, in an unrelated gang retaliation shooting, Ernest Tolliver was shot and killed as he sat in a car in a Homewood fast-food restaurant drive-through lane with his mother and a niece.

Ernest Tolliver, 15

Police ramped up patrols and Chief Nate Harper vowed to "dismantle" the Tre 8's and the North Charles Crips, the feuding groups police say cost Jolesa Barber her life. Police quickly arrested two people in connection with the North Side shooting and are seeking a suspect in the Homewood shooting.

But a sergeant with the city police Intelligence Squad said that in spite of these two high-profile incidents, gang violence is not on the rise.

"I can imagine that [there is] the perception that it is ... because you have two incidents that are relatively close together that involve young kids," said Sgt. Mona Wallace. "As far as I can tell, there's not a real upsurge."

Police say there are 40 or so street gangs -- ranging from six to 40 members -- in the city.

But dealing with the level that exists will take more than a show of police force, experts and community members' caution. The problem, they say, is complex, and more needs to be done to address the roots of the gang activity.

"I really don't know the answer," Sgt. Wallace said. "It's a culture that's becoming ingrained in people."

After last week's killings, authorities deployed multi-agency "saturation patrols" to flood the North Side and Homewood.

Police use such patrols throughout the year for drunken-driving checkpoints or nuisance bar roundups, and sometimes to quell hot spots -- areas of the city where crime has spiked.

"You get a big contingent of the department and all just flock to one area of the city," said Cmdr. Scott Schubert, who heads the Special Deployment Division as well as the recently reopened West End station. "You get as many arrests, as much intel and get as many bad guys and guns off the street as possible."

On Friday night, about 50 officers and federal agents headed out in teams to the North Side and Homewood. Included were plainclothes officers, zone patrol officers, members of the SWAT team, the Street Response Unit, sheriff's deputies, probation officers, liquor control officers and agents from the U.S. Drug Enforcement Administration, the FBI and the U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives.

Lt. Daniel Herrmann, of Major Crimes, said the teams move into an area to make contact with gang members and suspected criminals, sometimes just to talk to people on the street and other times to make arrests on outstanding warrants or probation violations. The show of force is meant to deter violence and gather information.

The problem, some veteran officers say, is that the effort is usually temporary and so are the results. Gang members will lie low during the patrols, as seems to be happening on the North Side. But once the police presence returns to normal, they will resurface.

Gang experts concur. George Tita, a professor of criminology at the University of California, Irvine who studied gangs in Pittsburgh in the 1990s and has continued to monitor the situation, said the effects of such blitzes don't last long.

"This is very effective for reducing crime in the short term," he said. "The problem is that it's hard to have any long-term deterrence."

Bishop Otis Carswell of the Potter's House Ministries Cathedral in Mount Oliver, a former gang member who works on violence prevention initiatives, said saturation patrols could potentially exacerbate violence.

"I believe it just stirs [the gang members] up," he said. "I believe it adds fuel to the fire."

Malcolm Klein of the University of Southern California who has researched gangs extensively, said that top-down police tactics do not work because gang violence is sporadic.

"Saturations or increased patrols are not going to be very effective since the shootings are unpredictable," he said.

"Police have a very limited capacity to do anything about street gangs," he said.

Tempering this view is Alfred Blumstein, a criminologist at Carnegie Mellon University, who said that sustained, coordinated violence suppression tactics that "mobilize different parts of the criminal justice system" are what's needed to make a long-term impact on gang violence.

Dr. Blumstein pointed to "Operation Ceasefire" in Boston, implemented in 1995 to reduce gang violence. Like saturation patrols, the operation used federal, state and local agencies. But it coordinated its efforts through a steering committee that met weekly and cracked down regularly and consistently, not just in response to spates of violence.

"My sense is it takes a concerted effort with an effective steering committee of a senior police official, a senior probation official and a senior prosecuting official," he said.

Dr. Tita also named Operation Ceasefire as a model for successful gang violence suppression. He added that "retail messaging" -- driving home the message to gangs that there will be severe consequences for violence and delivering on threats of crackdowns -- proved effective in Boston.

"It has to be a sustained effort and you have to follow through on the promise part of it," he said. "You need to make it clear to the youth in the city that if you are a part of a violent group ... we are going to bring our resources down on you."

Though experts and community members differ on how to tackle the existing problem of gang violence, they all agree that the best way to prevent future generations from engaging in gang violence is early intervention.

"First and foremost we need to get them early," said Bishop Carswell. "Once they've gotten older and they've gotten a taste of that lifesyle, it's hard to get them out."

Many of those who go into gangs "lack the knowledge of how to make a living legally," so job training and education is key, he said.

Sgt. Wallace believes there needs to be a change in the culture that glorifies the gangster lifestyle.

"You have to make the gangster lifestyle unattractive, whether it be through heavy enforcement or through prosecuting these groups," she said.

Dr. Tita believes a two-prong approach, suppression and intervention, is most effective. But he reiterated that whatever is done needs to be sustained, not just reactive.

"We've been down this road before in Pittsburgh," he said. "We have to stop participating only when it's a 12-year-old being killed. We have to participate when it's a 22-year-old high school dropout being killed. That life is valuable, too."