The background for 2012 shows Chicago had a large increase in homicides that year, with 506 victims—71 more than the prior year—linked in part to unusually warm weather early in the year and to changes in policing that included disbanding specialized units that had targeted high-crime areas.

Those shifts are described as contributing to more gang-related incidents and strains on law enforcement as the city moved toward community-based policing under Superintendent Garry McCarthy. If anyone knew Sergio, witnessed events on or before November 15, 2012, or has information about this case, please share what is known.