We propose a maximal covering location problem with a budget constraint to determine the optimal location of facilities that provide fast police assistance to homicide hot spots, to mitigate criminal activity in Medellín (Colombia). We use the Google Maps Application Programming Interface (API) to estimate the average traveling times between police units and criminal spots and impose a budget constraint taking into account the project’s costs. Our procedure identifies how the optimal locations for fast reaction police units have a diminishing marginal coverage pattern when subject to loosened budget constraints.