Think tank says David Hartley may have been mistaken for cartel spy

The intelligence think tank STRATFOR has released a report (registration required) saying that low-ranking members of the drug cartel known as Los Zetas may have mistaken David Hartley and his wife for spies when they allegedly shot and killed him Sept. 30. The scouts became suspicious because Hartley's truck had Mexican license plates, sources told STRATFOR, and pegged the Americans for spies from the rival Gulf cartel.

A spokesman for the Tamaulipas attorney general's office told CNN it doesn't have any official information to release on the theory.

"STRATFOR sources say Los Zetas scouts, known as halcones, had identified the Hartleys' truck as it made its way to Falcon Lake and watched the two set out on their Jet Skis toward the Old Guerrero region," the report says. None of the sources in the report are identified. "Both Gulf Cartel and Los Zetas operatives have been known to conduct surveillance and countersurveillance operations on personal watercraft, so these scouts thus identified the Hartleys as possible Gulf surveillance assets, given their vehicle's license plate and their method and direction of travel on Falcon Lake."

Lower-level Zeta members were alerted, and they killed Hartley without consulting their superiors, STRATFOR's sources say. The sources say the cartel is now in damage-control mode and has probably destroyed the body.

An investigator on the case, Rolando Flores, was decaptitated and his head was sent to the Mexican military -- a message from gangsters to law enforcement to "stay out of their territory," Texas Gov. Rick Perry said.

Mexican authorities have said the investigator's death was not related to the Hartley case.

(Photo of Hartley's sister: AP)