On July 13, 2006, Martín Ríos opened fire on Cabildo Avenue in the Belgrano neighborhood of Buenos Aires, killing an 18-year-old man and wounding six others. The attack marked the final and most deadly incident in a 13-month spree of shooting attacks that had terrorized the affluent residential district. Ríos, who became known as the Belgrano Serial Shooter or the Belgrano Madman, had carried out multiple shooting incidents between June 2005 and July 2006, each one escalating in severity and drawing increasing panic throughout the neighborhood. His attacks targeted seemingly random victims on the street, making residents fearful of simply walking through their own community.

Ríos's rampage occurred during a period when Argentina was relatively unaccustomed to mass shootings, making his actions particularly shocking to the nation. The escalating pattern of violence and the apparent randomness of victim selection suggested serious mental illness, though Ríos had not been apprehended despite numerous incidents over more than a year. Law enforcement struggled to connect the attacks initially, allowing the perpetrator to remain at large far longer than in countries with more established serial crime task forces. The shooting spree demonstrated vulnerabilities in Argentina's police investigative capacity and information-sharing protocols.

The July 2006 mass shooting and Ríos's eventual capture sparked intense national debate about gun control laws and the treatment of mental health issues in Argentina. The case highlighted the dangers of allowing individuals with severe psychiatric problems access to firearms and raised questions about how many warning signs had been missed. Mental health professionals and legislators began examining whether existing systems for identifying and treating dangerous individuals were adequate. The incident led to increased discussion about stricter gun regulations and improved mental health services, issues that remained central to Argentine public safety policy debates in subsequent years.