At least 21 people, including a 12-year-old girl and other ordinary citizens, have been killed by warring drug gangs since Thursday in the western state of Sinaloa, in one of the worst spasms of violence in memory in a region long conditioned to narcotics-related savagery.
The wave of deadly mayhem began with the audacious daytime shooting of a dozen people in the capital, Culiacan, and continued during the weekend and into Monday. The deaths of innocents, including the young girl, who had just left a party, have terrified the public and left many questioning the effectiveness of the federal government's ongoing crackdown on drug trafficking.
"Sinaloa Bloodbath" read a headline from El Sol de Sinaloa, a daily newspaper. The article Monday on its website was accompanied by a photo of corpses slumped in the back of a bullet-riddled pickup truck. An editorial in Monday's national daily El Universal questioned President Felipe Calderon's decision to aggressively pursue the nation's drug kingpins, a strategy the United States has encouraged and backed with millions of dollars in assistance.
"Direct confrontation has only escalated the violence," the newspaper said. "The worst thing that can happen is for us to become accustomed to the dramatic daily count of deaths and kidnappings caused by narcotics assassins."
Authorities were still sorting through the carnage in Sinaloa as the body count continued to rise Monday. But law enforcement and Mexican media accounts provided a picture of the relentless violence:
* On Thursday, gunmen in Culiacan shot dead six people inside an auto repair shop and three more outside. The victims included a 61-year-old university professor and his son, 37, also a professor. Later confrontations between the gunmen and authorities left three police officers dead.
* Early Saturday in Culiacan, rival traffickers engaged in a shoot-out, using automatic weapons and bazookas in a neighborhood in the northern part of the city. Police reported no deaths or injuries in that 15-minute clash, but photos of the scene show the pavement littered with heavy-caliber shell casings and homes scarred with bullet holes.
* On Saturday evening in the beach resort of Mazatlan, gunmen shot to death a high-ranking police official, then stormed a restaurant in a popular shopping mall, where they held patrons hostage before escaping. No customers were killed or injured. Photos from local newspapers show terrified shoppers running from the mall.
* Early Sunday morning in the city of Guamuchil, eight people leaving a quinceañera party were shot to death in their vehicles while they waited at a stoplight. Among the dead were several teenagers and the 12-year-old girl. The guest of honor -- 15-year-old Maribel Lopez Marquez -- was also injured in the attack, according to police.
* Early Monday, suspected rival drug gangs clashed again in a residential neighborhood in Culiacan. Assailants attacked a home with Molotov cocktails, burned vehicles and opened fire with high-powered weapons. No injuries or deaths were reported. But there were unconfirmed reports of two more drug-related shooting deaths in Mazatlan.
The state, home to the so-called Sinaloa cartel, headed by Joaquin "Shorty" Guzman, has become a battleground for traffickers feuding for control of the drug trade. Calderon has sent 3,500 army troops and federal police to the region as part of a nationwide offensive that observers say has both helped and hurt the situation.
The effort has resulted in high-profile arrests as well as the seizures of large caches of drugs and weapons. But the removal of top leaders has set off a power struggle among underlings eager to use violence to establish authority.
"The old drug lords often acted as mediators" to keep the peace, said Jorge Chabat, a Mexico City-based security analyst. "The new, young guys are not disposed to negotiate."
Mexico's drug war remains extremely fluid. Across the nation, established trafficking alliances are fracturing and new ones forming. On any given day, even veteran observers have difficulty figuring out who is fighting whom.
Still, experts say some of the violence in Sinaloa stems from bad blood between cartel leader Guzman and the Beltran Leyva brothers -- Hector Alfredo, Carlos Alberto and Marcos Arturo. Known as "The Three Gentlemen," the siblings for years were confidants of Guzman.
The rumored power struggle burst into public this year with the arrest of Hector Alfredo. Nicknamed "El Mochomo," for a desert ant with a vicious sting, he is alleged to be involved in money laundering and payoffs to corrupt officials. He reportedly was carrying $90,000 in cash and a cache of pricey wristwatches when he was seized in Sinaloa by elite military forces in January.
According to a popular law enforcement theory, the Beltran Leyvas believe that Guzman ratted out their brother and have retaliated with a vengeance. Unidentified assassins shot and killed Guzman's son Edgar, 22, and two friends in a Culiacan parking lot in May. Other Guzman relatives and associates have been captured by authorities, ostensibly with the help of tips provided by the Beltran Leyva brothers.
"Factions of the Sinaloa cartel are fighting each other," Chabat said. "That's why we're seeing all this violence."
Chabat said the cartels might be violating a long-standing custom to avoid civilian casualties in order to put pressure on Calderon to back off. Although polls have shown that the president's tough stance has largely been popular with the public, recent events may be changing minds.
"The situation is out of control," said Gerardo Contreras, manager of a shoe store in the mall were people were taken hostage. "The people of Sinaloa ask the president to stop this violence. The killing of innocent people can't continue."