US authorities and outraged Texans are pondering a plan of action to deal with Mexican pirates after a US jet skier was shot Thursday and his fleeing wife chased onto the US side of a border lake.

The shooting on Falcon Lake, part of the Rio Grande watershed near Zapata, Texas, follows a months-long surge in attacks by drug-cartel-linked pirates on US boaters who have crossed into Mexican waters. It is the first instance in which an American has been hurt.

"Piracy on Falcon Lake is an incredible story, especially when Somali piracy has been so much in the news," says Robert Chesney, a national security and terrorism expert at the University of Texas School of Law, in Austin. "It's amazing to think that it's actually happening on the Texas border."

Officials say the surge in attacks is a direct outcome of pressures on the cartels, both from law enforcement and competing cartels, that has pushed drug smugglers to diversify to supplement their incomes. The pirates are members of the violent Zeta gang, primarily deserters from the "federales" and other Mexican law-enforcement agencies, who used to be the enforcers for the Gulf Coast Cartel before essentially staging a coup and taking over much of the cartel's drug-running.

The pirates, brandishing AK-47s, so far have confronted and robbed five US bass-fishing boats that have wandered into Mexican waters, which the Americans are allowed to do on the jointly administered lake. In some of those instances, the Zeta pirates have identified themselves as "federales," but their well-known and visible Z tattoos indicate that they're brigands, not Mexican officials.

On Thursday, a couple from McAllen, Texas, rode their jet skis into Mexico to take a look at a favorite tourist spot, a famous church in Old Guerrero. At around 2:30 p.m., on their way back, six gunmen in two boats approached the pair. The man, David Michael Hartley, was shot as the two sped away while his wife, Tiffany Hartley, sped to a nearby lakeside home to ask for help, said Zapata County Sheriff Sigifredo Gonzalez. The couple never spoke to the gunmen, authorities add. A search for Mr. Hartley continued Friday.

"They saw them approaching and started revving it up back to the US side," Gonzalez told CBS News. "The guys just started shooting at them from behind."

But as US and Texas authorities continued to search for the missing Texan on Friday, pressure rose on law enforcement and the US government to protect US boaters. The shooting also provides a poignant, and unusual, reminder for many Americans of the proximity of some parts of the US to Mexico's escalating drug war, which has claimed, by some estimates, 26,000 lives since it began in 2006.

The 100,000 acre Falcon Lake is bisected by the Rio Grande's old river bed, which is marked by concrete columns. Created in 1954, it's managed by the bi-national International Water Boundary Commission.

Before the Zetas began robbing fishermen this year, the main international incidents on the lake were relatively minor: Mainly commercial Mexican tilapia fishermen laying nets in US waters and being chased by Texas game wardens.

But after the Zetas staged their coup against the Gulf Coast Cartel, tensions have heightened across the bucolic lake, heightened by the fact that a crackdown by Mexican authorities have forced cartels into rural areas. The lake is not only an ideal hiding spot, but is also used for marijuana smuggling.

"With all the feuding going on over there, the dope smuggling has dropped off and it is starving them," Jose Gonzalez, the Border Patrol's second-in-command in Zapata, told the Washington Post's William Booth in May. "This water is Zeta central. They controlled the whole lake. They distributed everything. Now they're desperate and diversifying."

Those who have encountered the pirates have feared for their lives. "I saw 'em, and I saw they were machine guns," bass fisherman Richard Drake told a local TV station in April. "They were that close, they were 15 yards from me. I was scared."

Locals say the jet ski incident is mystifying in some ways. For one, there are few jet skiers on the mostly fishing-oriented lake. And it's peculiar for jet skiers to wander so far into Mexican waters.

Even though a lot of violence in Mexico has happened close to US border towns, it's also unusual for cartels "to project force in the United States or against US persons, notwithstanding some high-profile incidents," says Professor Chesney.

"I think the larger significance of the story is it's yet another sign of the carefree violence and total disregard for human life and willingness to kill innocent bystanders'' by Mexican drug cartels, he adds. "For Americans, this is an insight into the inhumanity of the violence" in Mexico.

In response to intensifying border violence, President Obama sent 1,200 National Guard troops to the border earlier this year. Locals in Zapata say they have seen marine patrols increase since the first robberies in April. In light of Thursday's pirate attack, more enforcement on the lake is likely, locals believe. For now, the Texas Fish and Wildlife Department has issued a new warning, urging boaters to stay on the US side of the lake.

Tom Bendele, owner of Falcon Lake Tackle in Zapata, said he was confident US interdiction on the lake is "really going to step up."

But barring a ceasefire in Mexico, dangers are still likely to lurk on the otherwise placid waters of Falcon Lake, US authorities warn.

"The problem is is that securing an international water border is a lot easier said than done," Chesney says.