A Mexican police commander investigating the reported shooting of an American tourist on a border lake plagued by pirates has been decapitated and his head was found in a suitcase, a Texas sheriff says.

The death of Rolando Flores, commander of state investigators in Ciudad Miguel Aleman, was a message from gangsters for investigators to "stay out of their territory," Texas Gov. Rick Perry said. Flores was part of a group investigating the reported shooting of David Hartley on Falcon Lake.

"I think their attempt is to intimidate law enforcement, no matter who they are or where they are," Perry told The Associated Press.

Flores' decapitated head was found Tuesday in a suitcase outside a Mexican Army base, Zapata County Sheriff Sigifredo Gonzalez told the AP.

Cartels have used beheadings in the past to terrorize the public and send messages to Mexican law enforcement. U.S. officials have said threats from drug gangs who control the area around Falcon Lake have hampered the search for Hartley, though divers have been in the lake searching this week. Hartley was reportedly shot Sept. 30 while touring the lake with his wife on Jet Skis.

That part of Tamaulipas state is overrun by violence from a turf battle between the Gulf Cartel and the Zeta drug gang, made up of former Mexican special forces soldiers, and both are battling the Mexican military.

The search for Hartley's body is expected to continue, although Gonzalez said it's becoming increasingly unlikely the body will be found.

Perry said investigators shouldn't back off because of threats such as Flores' slaying.

"The worst thing we can do is let the terrorists dictate the terms of how we're going to live."

Instead, he said, the threat should be handled by increasing "the numbers of law enforcement and military."

Ruben Rios, a spokesman for the Tamaulipas state prosecutor's office, said authorities "don't know how or why he was killed. We don't have any details on how he died."

But Gonzalez said later Tuesday that "reliable sources within the law enforcement community of Mexico" told him Flores' head was found Tuesday morning in a suitcase outside of an Army base.

Hartley's wife, Tiffany, said she and her husband were returning to the U.S. from photographing a half-submerged church in Mexico when they were attacked by pirates on speedboats. Hartley was shot and presumably fell into the lake. Tiffany Hartley said she tried to retrieve her husband's body and his Jet Ski but the pirates continued firing and she fled. Gonzalez has said he has an eyewitness who corroborates her account.

U.S. officials, particularly Perry, and Hartley's family have been pressuring Mexico to step up the search for Hartley and determine what happened.

Falcon Lake is a dammed section of the Rio Grande, 25 miles long and 3 miles across. Pirates have robbed boaters and fisherman on the Mexican side, prompting warnings to Americans by Texas state officials, but Hartley's death would mark the first violent fatality on the lake.

Dennis Hartley, David Hartley's father, expressed shock and regret at Flores' killing.

"I just, I'm in shock about this right now," he said from his Colorado home. "I really don't have any hope that David will be found. I really hate other people putting their lives at stake. We don't need more sons lost."

The Mexican Foreign Ministry says it has been using federal, state and local resources, including the military and helicopters, to search for Hartley's body and opened an investigation. Over the weekend, authorities named two possible suspects.

However, Rios on Tuesday said no suspects have been identified and wouldn't comment on why a state investigator had already named two suspects.

On Sunday, state investigator Juan Carlos Ballesteros, who is assigned to Ciudad Miguel Aleman, said police believe brothers Juan Pedro and Jose Manuel Zaldivar Farias may have killed Hartley. Ballesteros didn't answer calls seeking comment Tuesday.


Rodriguez reported from Mexico City. Associated Press Writer P. Solomon Banda contributed to this report from Denver.