Cruel, merciless and with a passion for violence, the Mara Salvatrucha gang is one of the world's most vicious gangs and is spreading internationally. It may have even reached Australia.
Also called MS13, the gang is known for its barbaric fighting, contract killing, drug trafficking, gang rape, people smuggling and desire to be known as number one for most murders.
The gang's members are recognisable by the extensive and symbolic tattoos covering their face and torso, although newer members are eschewing the markings which make them more easily identifiable to police.
Gang members use hand signals such as the symbol for a devil's horn to greet each other, and initiation to become a "homeboy" or full gang member involves being kicked and beaten.
The gang exists in 42 US states, throughout the Central American countries of Mexico, Guatemala, Honduras, El Salvador, Puerto Rico, Spain, Canada and, some claim, Australia.
Reputed to have 100,000 gang members worldwide, the Salvatrucha recruits members as young as eight years old and punishes disloyalty with murder or maiming, such as cutting off a person's hands.
Gang weapons include every type of firearm, although some members prefer killing with a machete.
Notorious for their use of violence to inflict retribution and revenge, the cruelty of the Salvatrucha earned them respect and recruitment by one of the world's most powerful organised crime groups, Mexico's Sinaloa drug cartel.
While the core membership of the gang originated in El Salvador, whose capital San Salvador is considered the murder capital of the world, the gang sprang up in Los Angeles in the 1980s and has since spread from the inner-city to the suburbs.
In the US, MS13 has an especially heavy presence in Los Angeles and San Francisco, Washington D.C., New York, New Jersey and Houston, Texas.
The gang has become such a threat in North America, that US authorities began deporting as many members as possible back to Central America.
The Salvatrucha is so powerful in El Salvador, MS13 inmates have their own segregated jails which prison guards are too frightened to enter.
Salvadorean refugees from the country's bloody civil 12-year war, which ended in 1992 with a death toll of 100,000, formed the gang.
Between one and two million refugees emigrated to the US, with many gathering in the central LA neighbourhood of Pico Union.
They were not welcomed by the local Mexican-American gang M18, and formed Mara Saklvatrucha for solidarity and protection.
The gang's name is said to come from the Salvatrucha guerillas who fought in the civil war, and the slang word for gang taken from the marabunta, a fierce type of ant.
They entered into warfare with the Mexican-American M18 gang in the same neighbourhood.
The gang quickly multiplied and became one of the most organised and violently dangerous gangs in America.
The original membership included young men brutalised by the Salvadorean conflict, who said they simply "loved war" and wanted to wage it on the streets of their new country.
With guerilla training and experience in shooting people in the head point blank, the Salvatrucha soon out-terrorised the M18 gang.
As the gang expanded, refugees from other Central American countries were permitted membership.
In 1999, a 13-year-old Honduran refugee to Los Angeles, Brenda Paz joined a local chapter of Salvatrucha.
Paz ran away from home, ending up on the US east Coast in Virginia in 2002 where she and her boyfriend were arrested for car theft.
The 17-year-old agreed to become an informant on the gang in exchange for protection.
In a series of videotaped interviews the young woman described violent crimes, drive-by killings and life inside the Salvatrucha which "leads you to three places ... jail, the hospital or the cemetery".
She told investigators gang membership was "for life, you don't rat us out".
Paz was given a new name and a place on the federal Witness Protection Program.
But Paz found the isolated life of witness protection too hard to take and was lured back into the gang.
Meanwhile her imprisoned boyfriend was plotting her death from his jail cell while awaiting trial of the Diaz murder.
On July 17, 2003 a fisherman found the bloodied body of a young woman on the banks of the Shenandoah River in Virginia.
It was Brenda Paz. She was 17 weeks pregnant and had been stabbed 16 times.
The US practice of deporting violent Salvatrucha gang members back to their home country had a bounce back effect.
The deportees recruited new members from the streets of San Salvador and gradually, the gang made its way back to the streets of America via illegal immigration routes.
The practice caused an explosion of crime in suburban US neighbourhoods, causing the FBI to form a national taskforce to crack down on the gang.
But the gang has continued to grow in numbers and power.
In October 2012, the US Treasury Department announced a freeze on American-owned assets controlled by the gang and listed MS13 as a "Transnational Criminal Organization".
Central America has continued as a breeding ground for MS13 gang members.
The Penas Ciudad Barrios is a prison exclusively housing inmates from the Mara Salvatrucha gang.
The prison, built for 800, now houses 2500 prisoners who run their own 'society' complete with bakery and hospital.
In 2014, a decade after the Salvadorean government made the decision to segregate Mara Salvatrucha from the nation's other violent gang, Barrio 18, the decision was regarded as a failure which had only strengthened the gang.
The segregation had been prompted by one of the most violent prison massacres in the country's history, when 32 members from the two gangs died, some beheaded by their rivals.
"When we divided the gang members among jails, we began to strengthen them," El Salvador's security minister, Benito Lara admitted.
A truce made in 2012 between Barrio 18 and Mara Salvatrucha fell apart in 2014, and since then violence in the country has escalated.
El Salvador is one of the most violent countries in the world, according to United Nations which said it had a 2012 murder rate of 41.2 homicides per 100,000 inhabitants, and a projected murder rate for 91 per 100 thousand by 2015.
The country's proximity to North America and the family ties forged during the peak immigration of Salvadoreans to the US make law enforcement authorities fearful of the feeder effect to the gang's international expansion.