He grew up in Puerto Rico and played percussion in his high school band. He spent a decade working as a police officer and serving in the National Guard, part of that time as a peacekeeper in Egypt's Sinai Peninsula. And then he joined the U.S. Army. That was Ivan Lopez's seemingly unremarkable route into the military. But what happened from there — and why the 34-year-old soldier turned against his comrades at Fort Hood, Texas, with such deadly fury — baffled some of those who knew him.