Puerto Rico has for many years been an important transshipment point for drugs coming from South America and heading for the U.S., taking advantage of the islands’ status as a part of U.S. territory. The islands are less than a day away from drug-producing Colombia by speedboat. In 2003, the U.S. National Drug Intelligence Center said that most of the cocaine trafficked into Puerto Rico from South America was then transferred on to other markets, particularly the U.S. According to the report, wholesale sales of cocaine and heroin were often handled by Colombian and Dominican groups, as well as Puerto Ricans, while retail sales on the islands were often controlled by Puerto Rican groups.

However, a government report from 2007 said that there had been a significant decline in the use of Puerto Rico as a gateway for drugs into the country, and that this route now accounted for less than 26 percent of cocaine seizures arriving in the U.S.

Despite this declining importance as a transshipment point, Puerto Rico has seen a steady rise in violence in the years since 2008. Murder rates averaged 19 per 100,000 between 1980 and 2005, lurking at around 20 in the first few years of last decade, but increased to 22.5 in 2009 and around 24 in 2010. There has been a surge in drug-related killings in recent months, with more than 500 murders so far in 2011, putting the territory on course for a murder rate of around 26 per 100,000 in the year as a whole.

One example of this rising violence was a massacre some days before the raid, when four people were murdered in a drive-by shooting elsewhere in the capital city. Based on the way it was carried out, and the state of the victims, all of whom died on the scene, police said that the killing was carried out by “professionals who know how to use firearms and are involved in drug trafficking.”

The same 2007 U.S. government report also suggested that, even as shipments from Puerto Rico to the U.S. fell, smuggling onto the islands would increase. Authorities have said that the recent rise in violence is due to battles between drug traffickers over territory. The gang based in La Perla appear to have been mostly involved in catering to the local market, and authorities said that they were the biggest heroin suppliers in the territory, with a turnover of some $20 million.

A rise in smaller-scale, local drug trafficking could go some way towards explaining the increase in violence. A recent opinion piece in local newspaper El Nuevo Dia said that Puerto Rico was becoming a “narco-society,” due to the penetration of drug traffickers in politics, and the increases in drug consumption, pointing out that traffickers’ battles over sales points are at the root of soaring murder rates.