One night in late June, four black cars intercepted a truck on a highway 25 miles out of Rio de Janeiro. The hijackers, in well-practiced precision, disabled the truck’s tracking system, trained their rifles on the driver and ordered him to follow them back to the city to a favela named Chapadao.

There, the hijackers quickly transferred the truck’s load—such goods as electronics and textiles worth a total of $440,000—to a waiting vehicle. The transfer complete, it disappeared in the hillside neighborhood’s winding, narrow streets crammed with small brick homes, according to the police report.