MEXICO CITY  It had been an elaborate farewell to one of Mexico’s fallen heroes.

Ensign Melquisedet Angulo Córdova, a special forces sailor killed last week during the government’s most successful raid on a top drug lord in years, received a stirring public tribute in which the secretary of the navy presented his mother with the flag that covered her son’s coffin.

Then, only hours after the grieving family had finished burying him in his hometown the next day, gunmen burst into the family’s house and sprayed the rooms with gunfire, killing his mother and three other relatives, officials said Tuesday.

It was a chilling epilogue to the navy-led operation that killed the drug lord, Arturo Beltrán Leyva, and six of his gunmen. And it appeared to be intended as a clear warning to the military forces on the front line of President Felipe Calderón’s war against Mexico’s drug cartels: not only you, but your family is a target as well.

Prosecutors, police chiefs and thousands of others have been killed in the violence gripping Mexico, with whole families sometimes coming under attack during a cartel’s assassination attempt. But going after the family of a sailor who had already been killed is an exceedingly rare form of intimidation, analysts say, and illustrates how little progress the government has made toward one of its most important goals: reclaiming a sense of peace and order for Mexicans caught in the cross-fire.