Since transitioning from a civil war (1980-1992), El Salvador has been struggling with high levels of violence. With one of the highest murder rates in the world, the country is considered one of the most violent places outside a war-zone. A lot of attention has been directed towards the phenomenon of youth gangs, which is considered one of the main drivers of the high homicide rate. This thesis takes another approach and explores the role of police brutality in the escalation of violence. In the year 2012, 33 people were killed by the police. However, in 2016, more than 600 civilians were killed. Many of these deaths are considered to have been extralegal executions. This thesis asks the question: why did the security officer’s use of lethal force increase to such high levels between 2013 and 2017? To answer this, the thesis adopts an interpretive approach, seeking to understand the increase in police brutality through key actors’ perceptions of it. It relies on data gathered from qualitative interviews, conducted during a three-week field trip to San Salvador. The thesis argues that no single variable can explain such an extreme increase in the use of lethal force by security officers. By applying Müller’s crime-violence-governance nexus, the thesis analyzes the increase as a dynamic process of conflict escalation between gangs and the police. The conflict dynamics are influenced by some structural drivers, which enable such high levels of police brutality to develop. However, it is triggered by a series of key events that have transformed the gangs and their relationship to security officers. The thesis concludes that the increasing levels of lethal force between 2013 and 2017 should be understood as the result of a conflict transformation, where what used to be gang violence has mutated into what is increasingly an undeclared war between the public security forces and the gangs.