Mexican authorities have confirmed that 20 people were killed when a group of gunmen stormed a cockfight, in a small town in the western state of Michoacán. Officials and witnesses described a choreographed massacre in which assailants in military uniforms arrived just after 10.30pm on Sunday night and opened fire with assault rifles at the crowds of primarily middle-aged men. Two small trucks, one of them branded with the logo for Sabritas, a potato chip company, were used to block the highway leading to the cockfighting arena. Video filmed by witnesses nearby captured the sound of machine gun fire, which could be heard several miles away. Photos leaked to social media showed the aftermath of the massacre, with barriers and chairs knocked over, and bodies scattered inside and outside the building. Mexican police told local media they found 19 bodies – 16 men and three women. Another victim died en route to the hospital. More than 100 shells from 7.62 caliber rifles littered the ground. The police also seized 15 cars that were on the scene. Mexican army and national guard troops were deployed on Monday morning to capture the assailants, but it remained unclear which of the region’s many organized crime groups they belonged to. Cockfighting, while illegal in many areas, remains a popular pastime in parts of Mexico, though the fights between roosters are usually held clandestinely. Las Tinajas is a tiny pueblo of about 10 streets, close to Michoacán’s eastern borders with two other states, Guanajuato and Estado de México. The region has seen soaring rates of violence as smaller, local cartels fight for control over territory and smuggling routes with the Jalisco New Generation cartel (CJNG), one of the country’s most powerful factions, based in the neighbouring state of Jalisco. Last month 17 people attending a funeral in San José de Gracia, another small town in Michoacán, were murdered in broad daylight, also by gunmen wearing camouflage and bulletproof vests. In that incident, the gunmen arrived in white vans, pulling people from the event, before lining them up against a wall to shoot them. The hitmen took the bodies with them and cleaned up the scene before disappearing, leaving evidence of the shootout, but no complete human remains. After the slaughter in San José de Gracia, Mexico’s president, Andrés Manuel Lopez Obrador, said he wished “with all my soul” that the shooting had not occurred. “I wish it weren’t true.”