Drug gangs likely responsible for most of Chicago`s violence - Chicago News and Weather | FOX 32 News

Those actually shot or killed are not the only victims of violence in Chicago. The University of Chicago estimated the total cost at a mind-boggling $2-1/2 billion a year. Violence is a crippling burden on the local economy: wrecking neighborhoods, scaring away residents and jobs.

SEE: 8 dead, 41 wounded in weekend shootings

Fewer than 2,000 utterly ruthless, well-armed bad guys may be causing a majority of Chicago's homicides. They're shooting and killing each other, motivated in part by profits from illegal drug sales, according to a veteran criminologist who has worked closely with the Chicago Police Department.

When they began rounding up 41 leaders of a notorious gang last week that allegedly grossed $11 million a year running open-air heroin and cocaine markets on the West Side, it was hailed as a law enforcement landmark, the first use of a new Illinois law designed to target a small cadre of the most violent criminals.

"There's probably 1,500 to 2,000 that are in a network of individuals that are continuously interacting in a negative way and at risk of shooting someone or being shot themselves," Professor Dennis P. Rosenbaum says.

Though he sometimes speaks like the UIC college professor he is, Dennis Rosenbaum has worked closely with the Chicago Police to understand the city's bloody-minded drug gangs. Rising to rule a gang requires an utter ruthlessness, emulated by the wannabe's in gang-dominated neighborhoods, especially in warmer weather when more residents are outside, watching.

"The smallest things can set this off," Rosenbaum says. "People can be disrespectful of someone else's girlfriend, because all these kids have going is their street credibility. And they will fight and die for that."

Rosenbaum's short-term solution calls for courage on the part of the law-abiding.

"Everyone needs to come out and not just the kids who are at risk of shooting," Rosenbaum says of ending the shootings. "And these kids also need other things to engage them in the community. There needs to be other activities that go on that keep them from congregating."

Professor Rosenbaum is an expert in crime hot spots, a strategy that Chicago police are using.