Some 20-odd years ago I was living in Guatemala, and worked as Receptionist/administrator in a Spanish language school; part of the job was giving prospective students tours of the premises and explaining how lessons worked etc. One day an American turned up (not unusual) who practically screamed "military" from his every pore, not unusual in itself - even soldiers have holidays, and he wouldn't be the first I had encountered (off the top of my head I remember running into a British lady, a Swiss bloke and an Israeli who were all military types, and were just on holiday). However, this American made me feel really uncomfortable, although he was perfectly friendly, his eyes were dead. Even more unusually, he had a Guatemalan "shadow" who he introduced as his friend. I greeted his "friend" in Spanish, and would expect the usual formal greeting in return (Guatemalans are quite conservative). The Guatemalan "friend" looked very uncomfortable talking to me, and just muttered "buenas" as a greeting before shiftily looking away. From that point on he said nothing, he also gave me a very strong impression of being military, and also had dead eyes. I was getting some very bad vibes off both of these people, and had the very strong, if irrational, feeling that they had done some very unpleasant things to people. I gave the tour, but just wanted rid of them, and hoped they wouldn't choose the school I was working in. The American evaded all my questions about what he did or why he wanted to learn Spanish. In the end he did choose the school, I new his teacher fairly well, and she told me that she was unable to get any personal information out of him in the weeks he studied, which is highly unusual, and never found out what his job was. There was something about this American and his Guatemalan companion that screamed "DANGER" to every fibre of my being. I can't explain that feeling, but I do trust it.