It was a scenario U.S. law enforcement had long feared: A fragmentation grenade from Mexico's bloody drug war tossed into a public place.
Only the grenade thrower's bumbling prevented bloodshed in a south Texas bar — he neglected to pull a second safety clasp. But the act was proof that one of the deadliest weapons in Mexico's drug battle is a real threat to the U.S., and investigators are stepping up efforts to make sure it doesn't happen again.
While Mexican drug violence has been spilling across the border in the form of kidnappings and killings, grenades are a particular worry because they can kill large numbers of people indiscriminately, and they are a weapon of choice among Mexican cartel members.
"It's one thing to shoot someone — that's a very violent act. But to throw a grenade into a crowded bar or a crowded restaurant, that's a different type of criminal you are dealing with, a different mindset," said Bill Newell, special agent in charge of the U.S. Bureau of Alcohol, Tobacco, Firearms and Explosives in Arizona and New Mexico.
Mexican grenade attacks
In Mexico, there have been countless grenade attacks against police and rivals. Nearly a year ago, three alleged drug hit men threw several grenades into crowds of Independence Day revelers, killing eight people and wounding 106 others in an unprecedented attack on civilians.
The weapons are preferred by drug hitmen because they are cheap and easy to find. Many are left over from Central America's civil wars and sold on the black market to drug cartels. Some are brought in by weapons smugglers. Others are diverted from the region's militaries: In April, Guatemala seized 563 grenades after a shootout with Mexican drug cartel members, and officials later determined the grenades came from Guatemalan military bases.
The Mexican government says 1,600 grenades were seized in Mexico last year, a 170 percent increase from 594 in 2007. Already, 950 grenades have been recovered this year.
And there is evidence that those grenades are making their way north.
Markings on weapons match
The grenade that failed to explode in the bar in Pharr, Texas, had the same markings as grenades thrown in October at the U.S. consulate in Monterrey, Mexico, and at a television station in early January in the same city. The grenade thrown at the consulate failed to explode, and no one was injured when the grenade hit the Televisa network's studio as it aired its nightly newscast.
But all three grenades were manufactured at the same time and place, and were at one point together in the same batch from South Korea. Their manufacture date was unavailable.
The United States and South Korea rank as the top two producers of the grenades seized in Mexico, according to the ATF.
Grenades were mostly isolated to southern Mexico in the early days of the drug war and gradually moved northward as the government's attack on the cartels intensified and drug traffickers sought heavier arms.
American firearms agents began taking a harder look at the grenade threat from Mexico after explosives popped up at spots not far from the U.S. border.
Explosives found in border homes
The Mexican military seized 165 grenades and 14 sticks of TNT belonging to the Gulf cartel in the November raid of a house in the border town of Reynosa, Mexico, a dozen miles south of McAllen, Texas. That same month, grenades were used as diversions in the fatal ambush of a state police chief a few miles south of Arizona in Nogales, Mexico.
The alleged gang member who threw the South Korean grenade into the Texas bar on Jan. 31 wasn't believed to have been acting on behalf of a cartel. Still, Hidalgo County Sheriff Guadalupe Trevino, whose office investigated the case, suspects there is a loose association between the gang behind the attack and Mexican cartel members.
After the grenade bounced off the floor and landed on a pool table, an off-duty police officer picked it up and threw it back out the door. No one was hurt, no arrests were made, and authorities are divided about whether the targets were rival gang members or off-duty police officers.
The incident led the ATF to issue a warning to law enforcement agencies along the border.
"We shared it with our deputies right then and there. We cautioned them that while it hasn't happened here, it could happen here," said Capt. Eben Bratcher, a spokesman for the Yuma County Sheriff's Office along Arizona's border with Mexico.
Criminals avoid targeting civilians
Criminals using grenades in the United States would mostly likely target people tied to the criminal world, rather than civilians. Cartel bosses wouldn't likely approve of grenade attacks on U.S. law enforcement, fearing that a strong push-back from the United States would disrupt business, U.S. law enforcement officials and security experts said.
In Mexico, cartels usually toss grenades at police and military outposts and rarely have thrown them into crowded businesses or other public places.
Grenade attacks north of the border would more likely be carried out by rogue cartel members or homegrown gang thugs who assist cartels in home invasions and other crimes north of the border, law enforcement officers said.
"What's to stop some hothead from going off on their own and lobbing grenades at U.S. law enforcement officers?" said T.J. Bonner, president of the National Border Patrol Council, a union representing 16,000 U.S. Border Patrol agents.
ATF trains Mexican authorities
The ATF feels so strongly about the threat grenades pose to the United States that they have sent bomb technicians to Mexico, Guatemala and El Salvador to train authorities there to identify and track grenades.
The grenades sold legally to help U.S. allies in the region are snatched by corrupt soldiers who get paid by former colleagues, then cover their tracks by altering paperwork. Grenades then wind through Central America and Mexico, selling for $100 when bought individually and $50 apiece when purchased in bulk, according to the ATF.
ATF officials said the United States keeps tight controls over its own grenade inventories and that it knows of no grenades recovered in Mexico that were taken directly from American military supplies.
Scott Stewart, a vice president for the global intelligence firm Stratfor and a former diplomatic security agent for the State Department, said an even more daunting challenge in trying to prevent grenade smuggling into the United States is the porousness of the border.
"If we have bales of marijuana coming in and kilos of cocaine coming in, it's hard to guard against a handful of grenades," Stewart said.