The gruesome murders were each more than 1,000 miles apart, an arc of bloodshed that spanned much of the North American continent.

On a rutty street near a crowded slum in Honduras, gunmen sprayed automatic weapons fire at a bus filled with Christmastime shoppers. Twenty-eight people, including six children, were killed.

In the woods near Dallas, an innocent 21-year-old man was shot in the head, his remains eaten by animals. His pants were pulled down, and police suspect that he may have been sodomized.

And near the banks of a quiet river in Virginia, a 17-year-old informant was hacked to death. She was four months pregnant and stabbed 16 times in the chest and neck.

The killings were similar not only in their brutality but also in their lineage: Authorities say all three incidents are tied to a single Los Angeles branch of Mara Salvatrucha, a street gang formed 20 years ago in the immigrant neighborhoods west of the downtown skyline.

Today, the gang's extreme violence, vast reach and increasing sophistication have made it a top priority at the highest levels of law enforcement and political leadership from Washington to San Salvador.

In recent months, the departments of Justice and Homeland Security have launched a series of initiatives to confront the threat posed by the gang, also known as MS-13, which has between 30,000 and 50,000 members in half a dozen countries, including up to 10,000 members in the U.S., according to federal law enforcement estimates.

The FBI's creation of an MS-13 task force, the first nationwide effort targeting a single street gang, was ordered by Director Robert Mueller after several high-profile murders blamed on MS-13 in the suburbs of Washington. On Tuesday, Homeland Security's Immigration and Customs Enforcement agency for the first time placed an MS-13 member on its most-wanted fugitive list. The Los Angeles gang member is suspected in a string of violent crimes.

In Honduras, four Central American presidents gathered last month to address the gang crisis. Citing the destabilizing influence of groups like MS-13, they appealed for economic aid to curb the poverty and joblessness fueling the growth of gangs.

Authorities are scrambling to contain forces unleashed in part by past U.S. policies. Refugees formed the gang in the 1980s near MacArthur Park, just west of downtown Los Angeles, after fleeing a U.S.-backed civil war against insurgents in El Salvador. As the gang grew, immigration officials began a decade-long campaign to deport members, including ex-convicts and hardened leaders who helped spread MS-13 across Central America and solidify its structure.

In the United States, the gang has spread from California into 33 other states and the District of Columbia. Investigators say members are involved in murder, extortion, drug dealing and witness intimidation. The expansion has come from migration as well as from calculated efforts by its Los Angeles leaders to tap new markets of criminal activity. In Seattle, for instance, gang members arrived from Los Angeles in 1997 to distribute marijuana, heroin and crack cocaine, according to investigators.

"Everywhere you turn these days, you're hearing about MS-13," said Assistant FBI Director Chris Swecker, who is overseeing the nationwide task force targeting the group.

Traditionally, the gang's loosely structured leadership has been dispersed among a vast federation of cells that often act independently.

Although it remains unclear how well organized the gang's leadership is, Swecker recently told Congress that there were signs of greater cohesiveness within MS-13.

Times interviews with law enforcement officials in four countries and reviews of intelligence reports, letters between MS-13 members, transcripts of phone conversations and surveillance videos show that gang members communicate and coordinate criminal activity across state and international borders.

Gang leaders in the U.S. and El Salvador have shared information on informants, discussed punishing rivals and plotted an ambush to free an accused murderer, these records show. In one instance, dozens of MS-13 members from several East Coast states were videotaped meeting in a Virginia park.

In Central America, the gang allegedly targeted top government officials and law enforcement leaders.

"If these criminals are capable of killing 28 innocent people," Honduran President Ricardo Maduro said in an interview, "they are capable of anything."

Now, law enforcement crackdowns in Honduras and El Salvador are helping reverse the flow. MS-13 gang members recruited in those countries are making their way to the U.S. and bolstering the gang's ranks from California to Maryland.