Instead, López’s arrest sparked one of the most audacious displays of narco firepower in recent months. Sinaloa cartel sicarios unleashed chaos on the streets of Culiacán, overwhelming security forces in a ferocious running battle which left eight dead and 20 wounded . Spectacularly outgunned, pinned down by .50-calibre sniper fire and with the wreckage of burning, bullet-ridden vehicles littering a city paralyzed by fear, humiliated authorities were cowed into releasing their quarry.

Mexico’s Secretariat of National Defence (SEDENA) estimates almost a third of the two million firearms smuggled into the country in the last decade come from Europe. Some begin the journey as licensed exports from the E.U. to the U.S. where, with the help of ‘straw purchasers’ buying guns legally and feeding them to traffickers, they join the 200,000-guns-a-year torrent smuggled south.

From the safety of gleaming mansions in the foothills of the Italian Alps, government-owned munitions factories in Romania and Belgium, and boardrooms in Austria, Spain, Serbia, and the UK, Europe’s gun makers are reaping the bloody spoils of a catastrophic war on drugs, their weapons arming Mexican soldiers, cops and cartels alike.

A closer look at munitions intelligence from Armament Research Services (ARES), which analyzed the weapons used by cartel soldiers in Culiacán, points to some of that iron river’s myriad tributaries springing from sources thousands of miles away, far from the massacres, mass graves, and disappearances that punctuate years of narco conflict in Mexico. ARES identified Romanian-made AKs at the Battle of Culiacán, and said an FN Herstal MINIMI light machine gun (Belgian), plus handguns from Beretta (Italian) and Glock (Austrian) were also spotted during the series of firefights that day.

It’s a well-worn story that such decisive, military-scale cartel action is largely equipped by the seemingly endless iron river of blackmarket firearms trafficked illegally from the United States. But the traditional narrative of American guns flowing south to fuel the cartel wars, which last year contributed to 35,000 homicides, is only part of the picture.

Over the course of eight months shopping in a handful of Tucson, Arizona, gun stores and pawn shops, Michael Huynh and girlfriend Katie O’Brien bought enough hardware to tool up a small army.

Their haul of 16 AK-type and two .50-calibre rifles—plus a tripod-mounted machine gun—set them back over $30,000, and they traded the lot with Huynh’s heroin dealer for cash and drugs, who in turn had the guns trafficked to an organized crime gang in Mexico.

Among their stash were three WASR 10 assault rifles built by Romania’s state-owned arms factory, Romarm. This long-standing cartel staple—with its distinctive maplewood hand guard and stock—is regularly imported into the States by Century Arms, one of America’s largest and most controversial gun dealers. Century ignored repeated requests from VICE for comment.

Huynh and O’Brien’s contribution to the violence earned them five years in prison: gun trafficking in the States is not a federal crime, and while straw purchasing is, it tends to attract low sentences. While there’s no telling yet precisely where their guns ended up, the evidence from the Battle of Culiacán shows the significant role European brands play in Mexico’s drug wars.

Of course, European gun manufacturers eyeing up Mexico aren’t solely reliant on jonesing straw purchasers swapping guns with border smuggling rackets in exchange for drugs.