Maybe that's why I'm a bit shocked that you're shocked. These things have been going on for a long time and they're well documented. I'll just give three examples: the My Lai massacre, the imprisonment/trial of Omar Khadr (a child soldier) and the extrajudicial execution of Anwar Nasser al-Awlaki (an American citizen).
(To be clear, I don't think any of the above are justifiable. As a Canadian, I was particularly ashamed of Canada's position towards Khadr. But I don't go around a) thinking these things don't happen and b) that they're alway black and white)