The brazen pre-dawn slayings came just hours after the navy honored Melquisedet Angulo as a national hero at a memorial service.
"The message is very clear: It's to intimidate not only the government but its flesh and blood," said Jorge Chabat, a Mexican expert on drug cartels. "It's to intimidate those in the armed forces so they fear not only for their own lives, but the lives of their families."
Angulo was called an example of courage in the face of terror, reports CBS News correspondent Jeff Glor, but just hours after laying him to rest, his family became an example of the ruthless, savage ways of Mexican gangs.
At least a dozen men executed Cordova's mother, sister and aunt and critically injured two of his brothers - storming into their home and spraying the living room and bedroom with bullets, Glor reports.
Federal officials had warned last week's killing of drug lord Arturo Beltran Leyva, known as the "boss of bosses," could provoke a violent backlash from smugglers, who have gone after federal police in the past following the arrest of high-ranking cartel members. Experts predicted a power vacuum in his wake - and retaliation from cartels - but perhaps nothing on this scale, Glor reports.
Beltran Leyva was among the most-wanted drug lords in Mexico and the United States, and was the biggest trafficker taken down by President Felipe Calderon's administration so far. U.S. Drug Enforcement Administration officials blamed his cartel for much of the bloodshed across Mexico.
Even so, the country was shocked by the brutal slayings of Angulo's family at their home just hours after the fallen marine's mother, Irma Cordova, 55, attended his memorial service in Mexico City, where she received the Mexican flag covering his coffin.
His brother, Benito Angulo, 28, his sister, Jolidabey Angulo, 22, and aunt, Josefa Angulo, 46, also were killed shortly after midnight when gunmen wielding assault rifles broke down the door of their home. His sister, Miraldeyi Angulo, 24, was reported in serious condition at a hospital.
The family's home in southern Tabasco state was littered with more than two dozen bullet casings.
The revenge killing is a massive embarrassment for the embattled Mexican government. They had trumpeted the raid as a major step forward in their drug war. Leyva managed a quarter of the estimated $30 billion in illicit drugs that travel annually from Mexico to the United States, Glor reports.
Hit men linked to Beltran Leyva's cartel have a strong presence in Tabasco, a Gulf state bordering Guatemala, and were suspected of being behind the attack. State and federal forces searching for the assailants set up roadblocks across the state Tuesday.
The navy did not say whether it was taking special measures to protect marine families, including Angulo's two children, ages 3 years and 16 months. Authorities did not say where they or their mother were when their relatives were slain.
Calderon called the attack "a cowardly act" and vowed to press forward in his war involving more than 45,000 troops.
"We will not be intimidated by criminals without scruples like those who committed this barbarity," he said Tuesday. "Those who act like this deserve the unanimous repudiation of society and they must pay for their crime."
While the armed forces have led Calderon's crackdown against organized crime that has seen more than 15,000 people killed by drug violence since it began in 2006, direct attacks by cartels on troops are rare, especially for marines who only recently started playing a major role in the drug war.
Most of the killings have been among rival smugglers, according to the federal government. Hundreds of local, state and federal police also have been slain, but only a handful of soldiers have died at the hands of traffickers.
Angulo, 30, was the only marine killed in the Dec. 16 raid that sparked a nearly two-hour shootout at an apartment complex in the colonial city of Cuernavaca, south of Mexico City. Two other marines were wounded.
Angulo was also the only marine whose identity was made public of the more than 60 who took part in the operation, which also left six other gunmen dead in addition to Beltran Leyva. Mexican troops never have their names or numbers on their uniforms to protect their identities.
The Mexican government, eager to announce its victory, was unusually open about last week's raid, much of which was filmed by local media. Reporters were allowed into the apartment afterward to view Beltran Leyva's bullet-riddled body.
"This is really worrisome and is a challenge to the government because clearly one of the weapons of organized crime is its ability to use violence to intimidate, and that's where it has been apparent that the state has failed many times in protecting its officials and, in this case, even their families," Chabat said.
The Tabasco attack came exactly one year to the day after authorities found the bodies of seven decapitated soldiers and five other victims in southern Guerrero state, a region where the Beltran Leyva cartel has been battling for control. The bodies were accompanied by a sign that warned: "For every one of mine that you kill, I will kill 10." A bag of their heads, some still gagged with tape, was found nearby.
Those slayings, in Chilpancingo, an hour north of the resort of Acapulco, marked the worst attack against the Mexican army in its half-century battle against drug gangs.
After the gruesome discovery, the government held a high-profile ceremony aimed at reassuring the nation it would not surrender. Officials also released the names of the troops - just as the navy did Monday when it honored Angulo. Their sobbing wives appeared on national television receiving the flags that had been draped on their husbands' coffins.
In that case, however, officials ended the ceremony at the base and refused to say where the bodies would be buried; it also released no information on which cartel was suspected in the killings.
On Monday, by contrast, navy officials flew back with Angulo's family to bury him in his home state, where their arrival was covered by local media.