Police in the Mexican resort city of Acapulco said they captured the 19-year-old female leader of a local hit squad, while she was in the act of leaving a gruesome “narco-message” for rivals.

While following a vehicle they suspected of being used in a recent kidnapping, federal police in Acapulco witnessed a young man and women get out of the car, holding a cooler and several posters with warnings written on them.

Upon detaining the individuals, authorities made an unpleasant discovery: inside the cooler was a severed human head. The officials found another head inside the car, and placed the individuals under arrest.

According to the Guerrero Secretary of Public Security, the woman was the leader of an assassination ring in the service of an upstart local gang known as La Barredora. As InSight Crime has detailed, the larger cartels such as the Zetas and Sinaloa Cartel have lost their hegemony on trafficking routes in the city, and smaller groups such as La Barredora and the Independent Cartel of Acapulco have risen up to take their place.

As a result of this trend, the city has seen an unprecedented spike in violent crimes used to intimidate rivals.