CIUDAD JUAREZ, Mexico – Gunmen spraying automatic weapons fire killed seven people at a park that had been built as an anti-violence measure in the besieged Mexican border city of Ciudad Juarez, authorities said Monday. The assailants arrived during a soccer game the park in the Francisco I. Madero neighborhood and opened fire Sunday afternoon, said Carlos Gonzalez, a spokesman for the Chihuahua state prosecutors' office. Two of the people killed had been playing soccer. The body of one young man in his blue-and-red soccer uniform lay beneath a huge sign reading "Live Better" — the federal government's motto — and "Todo Somos Juarez," or "We're All Juarez" — the name of a program to reduce violence and improve life for Ciudad Juarez. Four people, including a 12-year-old girl, were hospitalized in critical condition, and one later died of his wounds. Investigators found 180 bullet casings from the sort of assault weapons typically used by drug gangs, Gonzalez said, though they had not yet identified the perpetrators or a motive. The park was inaugurated four months ago as part of the "Todos Somos Juarez" program. Ciudad Juarez, across the border from El Paso, Texas, is Mexico's most violent city, with more than 3,000 killed last year as the Sinaloa and Juarez drug cartels for control of lucrative trafficking routes into the United States. Running battles between soldiers and gunmen, meanwhile, left eight drug gang suspects dead outside the northern city of Monterrey, said Jorge Domene, spokesman for the Nuevo Leon state public safety department. Gang members used stolen cars to blockade 11 junctions of a road, a common tactic used by Mexican cartels to prevent security forces from sending reinforcements. Domene said the gunfight erupted in the town of Garcia, west of Monterrey. The gunmen fled and fought running battles with soldiers chasing them down a highway. The eight bodies were found in four towns along the road, Domene said. More than 34,600 people have been killed nationwide since President Felipe Calderon launched a crackdown against drug traffickers in December 2006. Meanwhile, a series of banners appeared Monday in the western states of Michoacan and Guerrero claiming La Familia drug cartel has decided to disband. "La Familia Michoacana is completely dissolved since it has been unfairly blamed," the banners read. "La Familia Michoacana has exterminated rapists and kidnappers and it's time for Mr. Felipe Calderon to investigate his Cabinet, most essentially (Public Safety Secretary) Genaro Garcia Luna." The gang has sometimes used banners draped from pedestrian bridges to deny responsibility for crimes or to send messages to authorities, but state officials said they could not immediately verify the authenticity of the new banners. The federal government said in December that the once-fearsome cartel had been "completely dismembered," breaking down into small groups that commit robberies to pay their members. The cartel has dominated crime in the western state of Michoacan for several years, making money by trafficking methamphetamine and extorting protection money from businesses. It has also become known for its bloody ambushes of federal police. La Familia has been thrown into disarray, however by the recent arrest and deaths of top members, including cartel leader Nazario Moreno, nicknamed "The Craziest One," who was killed in a shootout with police on Dec. 9.