If you have a serious mental illness you do not necessarily need to have gone through any traumatic environmental experiences to cause a crisis; your biochemistry does all that for you. It takes all environmental stimuli and warps them. Yes, it is worse if terrible things happen to you in your life, but you can have the perfect, ideal life and a serious mental illness will twist and warp whatever your experiences are. It is not usually the case that people are "driven crazy" by life or by other people; it depends on the amount of "resources" that your biology gives you in the first place. If you are prone (genetically) to a specific form of mental illness it takes fewer environmental "prompts" to cause problems. If you are lucky enough to be born without much in the way of a pre-determined genetic problem you can be in some pretty terrible environments and come out all right.
I went to graduate school with a woman whose parents had each been in a different Nazi death camp in WWII, and she was quite well-adjusted and her parents were two of the sweetest little old people you'd ever meet.
I also had a young college student in counseling from a very rich family (read: very, very, very, very, very rich) and she was suicidal because she did not get in the "correct" sorority. Another was upset because she couldn't figure how many people to invite to her parents' yacht for spring break. (Both true stories - details changed slightly to protect the identities - etc.)
Most of us are somewhere in the middle and need a combination of coping skills issues, a predetermined genetic disease process, and some environmental stressors to tip us over the edge.
The type of violence we see in a "violent ward" is usually the result of a schizophrenic or psychotic process (or a physiological process such as dementia, alcoholism, or drug use) and rarely the result of sociopaths, such as your Ted Bundy types. Those folks are generally much more self-controlled, especially in situations like this.
Gack! I sound like I am teaching class! Sorry 'bout that! :-)
[Blechhh!!! You are right - that WAS pretty disgusting, wasn't it? :-) ]