As night falls in Colombia's oil-rich province of Arauca los encapuchados - the hooded ones - emerge on horses, motorbikes or in flashy trucks with tinted windows.
Assassination, death threats and other forms of violent or psychological intimidation are the trademarks of these well-armed, faceless young men.
For five years los encapuchados and other paramilitary death squads have waged a dirty war against the civilian population of largely uneducated peasant farmers and their teachers in Arauca.
Local protest against the government's oil policy and demand for better social services and agrarian reform is viewed as subversive and is crushed by these paramilitary groups who are financed by local landowners.
ASEDAR, the Arauca teachers' union, has lost one leader to an assassin's bullet, another has "disappeared", one has been forced into exile and 43 members, including the entire executive committee, have received death threats. These come sometimes by telephone, sometimes in the form of an invitation to their own funeral mass.
The ASEDAR executive committee blames the discovery of oil in the early 1980s for their problems. Arauca was a farming region long abandoned by the state and teachers remember being paid in fresh fish and cigarettes.
The arrival of foreign oil companies revitalised the guerrillas who finance their armed liberation struggle by demanding huge "revolutionary taxes". This, in turn, brought the military to Arauca. They implemented a brutal US-designed counter-insurgency strategy known locally as "draining the fish tank". It was in the tank, according to the solicitor-general, that "a direct relationship is established between unions or organised peasant groups and the guerrillas".
In a country with a high illiteracy rate and poor state education , the Colombian teacher has a galvanising role beyond the classroom. And, according to ASEDAR leader Hernando Blanco, union activists are seen as enemies of the state.
"Anyone who doesn't think like the government is labelled a guerilla sympathiser," he said.
In a 1994 report, the Andean Commission of Jurists called Arauca "one of the most violent regions in Colombia" and described the atmosphere as one of permanent war.
Some locals hoped the blood spilt on Arauca's oil fields would not be in vain. But local government corruption has diverted millions of pounds of oil royalties away from social investment.
According to ASEDAR, 90 per cent of Arauca's Pounds 5 million education budget is spent on teachers' salaries (about Pounds 95 per month) leaving nothing for raw materials.
In 1994 the embattled administration of President Ernesto Samper promised a great leap forward for Colombia with social programmes financed by oil revenues and a genuine respect for human rights. But persistent allegations of drug corruption continue to sink the presidency and his good intentions.
Nevertheless, the education ministry recently revealed a 10-year plan to create a cradle-to-grave school system for all.
The chances of success seem remote. Samper is widely regarded as a lame-duck president and the military budget is seven times that spent on education and three times more than the entire social services budget.
Hernando Blanco sees no alternative to an indefinite strike. But this is fraught with danger. A teachers' strike would be considered illegal by the government whose hooded encapuchados would need little encouragement to break it.