Ciudad Juarez seven bodies were dumped before dawn Tuesday at a school soccer field in a leafy, upscale neighborhood in this Mexican border city.

Neighbors found the bodies — beaten, choked, in some cases mutilated and then shot — lined up along the field's fence. Alongside were three banners allegedly signed by a Mexican drug gang with messages directed at a rival gang, police spokesman Jaime Torres said.Hours after the bodies were removed, blood stained the curb, yellow police tape hung from the fence and classes continued at Colegio Sierra Madre, a private kindergarten-through-high school in a neighborhood of stucco homes, manicured lawns and palm trees.Only police in ski masks periodically drove past the campus, which posted an armed guard at the metal gate.Alejandro Pariente, a local prosecutor's spokesman, said the victims have not been identified, and they have no suspects.The homicides were the latest of hundreds of gruesome killings in Ciudad Juarez, where drug violence has taken a particularly heavy toll during Mexico's nationwide crackdown on the drug cartels that supply U.S. consumers.Also Tuesday in the border city of Tijuana, gunmen opened fire on a car in the parking lot of a Sam's Club, killing a woman and gravely injuring a man at midday, just as a nearby school prepared to let children out for the day, the state prosecutor's office said.These murders were among more than 4,000 drug-related killings this year in Mexico. Challenged by arrests, deaths, extraditions and new rivals, the cartels are brazenly attacking each other as well as police and the 20,000 soldiers President Felipe Calderon deployed against the drug gangs.Separately Tuesday, a Mexican businessman whose son was recently killed by kidnappers announced the creation of a group to encourage citizens to report crimes, fund security initiatives and compile criminal statistics.Alejandro Marti said his System of Observation for the Safety of Citizens aims to track how many reported crimes go unsolved."Crime has become one of the easiest businesses, with little possibility of getting caught," he said.The death of Marti's 14-year-old son Fernando inspired anti-crime protests across Mexico, particularly because prosecutors alleged that a police detective had been involved. The boy was found dead in a car trunk even though his family paid hundreds of thousands of dollars in ransom.Authorities acknowledge that the vast majority of kidnappings and other crimes go unreported in Mexico because people mistrust police. The government is also reluctant to release homicide figures regularly, making it difficult to grasp the true breadth of kidnappings, homicides and robberies in Mexico.