Despite a bloody drug war raging just across the border, some Americans living near Mexico act as if it's still a backyard playground.

In the last two weeks alone, two American tourists have been killed in Mexico in vicious attacks — one while riding a Jet Ski and another when his bus was hijacked. And a Mexican police commander investigating one of those deaths was killed this week, his severed head delivered in a suitcase to a local Army post.

But Texas officials keep encouraging boaters to enjoy the bass fishing on a border lake. And Gov. Rick Perry has not urged people to take any special precautions, suggesting only that U.S. and Mexican authorities increase the law enforcement presence in the area.

"There's like a psychological aspect to these kinds of warnings, that folks just don't take them seriously, or perhaps they believe the authorities are simply issuing these for liability reasons," said Fred Burton, vice president of intelligence for Stratfor Global Intelligence, which analyzes the drug war.

"There are people that say, 'Well, I know this area. I'm comfortable. Nothing will ever happen to me.'"

Tiffany and David Hartley may have been two of those people. They were working in Reynosa, a Mexican border town rife with drug violence, when Hartley's company moved them to McAllen, Texas, just across the Rio Grande, for safety.

The couple decided to take Jet Skis across Falcon Lake, which is divided by the border, to photograph a historic church. They were on their way home when pirates opened fire, killing David Hartley, according to his wife.

Just days later, a student from the University of Texas-Brownsville was shot and killed in Mexico. Jonathan William Torres, 19, was one of two people killed when his bus was hijacked in Matamoros, across the border from Brownsville.

David Hartley's father, Dennis, said his son was not aware of any violence on the lake.

"My son is a history buff. He wanted to get a picture of that church. Not hearing of any recent activity there, David and Tiffany decided to go there and snap some pictures."

The Mexican side of Falcon Lake, where David Hartley was last seen, is in the Mexican border state of Tamaulipas. On Tuesday, Tamaulipas Gov. Eugenio Hernandez Flores invited Tiffany Hartley to go to the area prosecutor's office and file a formal complaint about the alleged slaying with his guarantee of safety, according to The Monitor of McAllen.

In an interview on NBC's "Today" Wednesday, she said she would decline the invitation.

"We spent 4½ hours at their office (in the Mexican Consulate in McAllen), and we were assured that they were gong to get the paper work to Mexico City, to the authorities there, and they were going to be taking them to Reynosa the same day."

On Tuesday, she said she and her husband's family had appealed to the Obama administration for help in the search but received no response. On Wednesday, U.S. Homeland Security Department spokesman Matt Chandler extended the department's sympathy to the family and assured that Mexican authorities had been offered assistance in their search for Hartley.

The State Department has issued repeated travel warnings to Americans traveling to or living in Mexico, with a particular focus on the area just south of the border. The warnings say that kidnappings are occurring at "alarming rates" with U.S. citizens often the target.

In response, Texas universities have canceled their sponsored spring break trips across the border and have warned spring breakers at South Padre Island near the border not to cross into Mexico.

In May, the Texas Department of Public Safety warned boaters to avoid the international boundary that zig-zags through Falcon Lake, which is 25 miles long and 3 miles across at its widest point. The warnings came after men armed with assault rifles twice robbed fishermen on the Mexican side of the lake. They traveled in the low-slung, underpowered commercial Mexican fishing boats that are familiar here. They asked for money, drugs and guns, and took what cash was available. No one was hurt.

Even as the headlines carry grisly reports of murders and torture, thousands of Americans still trek across the border for work and to visit family.

"People here on the border go back and forth all the time," said state Rep. Aaron Pena, who represents a portion of the border near his hometown of Edinburg. "Many people have to go because they have family over there. Funerals happen, weddings happen, grandmas get sick or they have businesses over there. For many of them, they feel safe because they live it daily. But it can strike you in a moment."

In the days after Hartley disappeared, Texas officials stood on the shore of Falcon Lake and encouraged Texas boaters to enjoy the fishing on the American side. Officials insist the lake is safe, as long as boats stay in U.S. waters. The border is marked only by buoys.

"As far as I know, it's fine if you stay on the U.S. side," said Rob McCorkle, a spokesman for the Texas Parks and Wildlife Department. "Traditionally, it's been a very good bass fishing lake."

Still, Perry says many Texans living on the border, particularly farmers and ranchers, understand and respect the threat.

"I don't know that the city dwellers have engaged, but the rural dwellers, I promise you, the vast majority of those people understand the threat for their safety," Perry said.

The disappearance of Hartley and the decapitation of Tamaulipas State Police Commander Rolando Flores did not even make major news in Mexico, where the drug war has killed more than 28,000 people since President Felipe Calderon declared war on the cartels in December 2006. More than 2,000 of those have been police.

Leading Mexican daily El Universal noted Flores' death in the last two sentences of a story on violent events Tuesday in Tamaulipas state, including the kidnapping of four university students and a series of shootouts that killed 12 people.

"Unfortunately, this is nothing new," Perry said. "Mr. Hartley, the UT student murdered over there, now this commander, all this in a two-week period of time, and this is a direct threat to people in communities on the border, including Texas."


Associated Press Writer Alexandra Olson in Mexico City contributed to this report.