The homicide rate in Chicago has soared more than 50 percent in the first few months of 2012 over the same time period last year. The number of non-fatal shootings is up sharply, too. Why? Some say it could be just a statistical blip or due to rising temperatures, as Chicago had an extremely mild winter this year with record-setting warmth in March, the bloodiest month. But others say there is a deeply entrenched culture of violence in some city neighborhoods and within the prolific Chicago street gangs. They worry 2012 could be one of the most violent years in the city since the 1990s.