Authorities detained three alleged members of the Knights Templar drug cartel in the killing of one of Mexico's highest-ranking navy officers and a bodyguard, Attorney General Jesús Murillo Karam said Monday.

President Enrique Peña Nieto vowed the attack wouldn't go unpunished. "We will work with all speed to arrest and bring to justice everyone responsible for the death of Vice Adm. Carlos Miguel Salazar," he said.

The killings of the admiral and another naval officer serving as his bodyguard marked a rare attack on Mexico's top military brass, but appeared to have been the result of a series of tragic coincidences rather than a planned, targeted assassination.

Still, the shooting on a rural road in the western state of Michoacán showed just how out of control the state has become as the government offensive against crime gangs runs up against resistance from the Knights Templar cartel.

Salazar, his wife, driver and bodyguard were returning from a visit to the admiral's family in the Mexico City area, when they ran into a protest that had closed the main highway leading back to the naval station he commanded on the Pacific coast, near the resort of Puerto Vallarta.

Seeing the protest, the admiral apparently made a tragic mistake. Rather than waiting for the road to reopen, as dozens of other vehicles did for about two more hours, or turning around and heading back to the nearest city to catch an airline flight, he had his driver head down a rural two-lane road in search of a shortcut.

"He decided to take an alternative route, to get back to his job on time, and he took a secondary road for that purpose," Murillo Karam said.

But Michoacán has become a hotbed of cartel violence, with at least a half dozen ambushes of federal police convoys last week. And the highway blockage wasn't just any protest.

A reporter for a Michoacán newspaper saw the protesters, mainly taxi and bus drivers, holding signs saying "Get out, Federales" and "We demand federal forces get out of Michoacán." Such protests have frequently been organized by the Knights Templar cartel, which has often forced or paid residents to take part.

Federal security spokesman Eduardo Sanchez said it seemed unlikely the protest could have been organized just to interrupt the admiral's travel. Rather, it appeared a response to the two-month-old government buildup of army and federal police in Michoacán after a series of towns rose up in arms and formed self-defense groups to fight off pervasive abuses and extortion demands by the Knights Templar.

Salazar's SUV had navy logos, but inexplicably was not bulletproof. Neither he nor his bodyguard was in uniform.

Murillo Karam said one vehicle cut off Salazar's SUV, forcing his driver to stop. A second vehicle full of armed men then drove up and opened fire. Salazar pushed his wife to the floor of the SUV and she escaped with only minor injuries, but the driver was severely wounded.

Murillo Karam said that the three suspects were detained in one of the vehicles used in the attack and that they had admitted belonging to the Knights Templar and taking part in the attack. He quoted the suspects as saying the cartel paid them 7,500 pesos a month (about $600) to steal, kidnap and extort money from people.

The navy has not been as heavily involved in the anti-drug fight in Michoacán as it has been in other states.

Michoacán has proved the toughest challenge yet for Peña Nieto, as it was a major predicament for his predecessor, Felipe Calderón, who started off Mexico's drug war in late 2006 by sending troops to Michoacán. The near-totalitarian control exercised by the Knights Templar over Michoacán only grew under Calderón's administration.

So far Pena Nieto's government doesn't seem to have a different strategy than Calderón's for the complex, bloody, multi-sided battle in Michoacán that pits the pseudo-religious Knights Templar against police, vigilante groups and the rival New Generation Jalisco cartel.

"Our town is practically occupied by federal police, and it's strange: We just wonder how with this kind of presence, there is still so much violence," said a masked Indian farmer from the most recent community guard group to spring up, in the Michoacán town of Los Reyes.

"This is a mystery," he said. "Is it because they (police) don't have the necessary ability, the intelligence information, or the strategy?"

The farmers held a news conference Monday in Mexico City, but refused to give their names or show their faces for fear of reprisals from the cartel.

The Indian farmers formed a unit to patrol their communities in March after cartel gunmen began demanding protection payments of 2,000 pesos ($150) per hectare (2.247 acres).

A week ago, several people were killed by suspected cartel gunmen when they protested in the Los Reyes town square against continued drug violence.

Follow us on twitter.com/foxnewslatino
Like us at facebook.com/foxnewslatino