I'm chilean, andi studied this at school and in college.
In 1969, Salvador Allende, a very socialist guy anounced he'd run for president, he wanted to impose the cuban model DEMOCRATICALY. Extremists groups such as MIR (Movimiento de Izquierda Revolucionaria) didn't like that. And the Left was divided.
In 1970 Allende won the elections, people within allende's goverment started to leave, and the left groups impulsed by the cuban revolution started to grow. Allende couldn't handle it and chile started to go crazy.
In 1973 the Armed Forces organized a coup d'état, it was succesfull and the army's general, Augusto Pinochet, took over the country.
The following days after the coup d'état, (September the 12th and 13th), There were alot of guerrillas between the MIR (who were training in cuba during allende's goverment) and the intelligence service (the DINA). The DINA (of course) "won" the guerrillas, and started torturing MIR people to "get information". MIR dissolved and they moved over and they started torturing ALL the comunists, then the socialists, and later they started torturing random people for no reason (my grandfather was tortured for example) That went on for 5 years.
After those five years Pinochet replaced the director of the DINA with someone less sadistic, and the torturing decreased (it didn't really stop)
I'm thinking maybe Gus was a torturer, or was a member of "La caravana de la muerte", a caravan which went from town to town murdering communists, or maybe he was a MIR guerrillero.
I don't remember in which year Gus left chile, because alot happened later, like the communist army, and the cuban weapon ships.
PS: I'm chilean, so, English is a second language, this text above is probably full of grammar errors, sorry for that.