I finally found help when I got him to the Alzheimer's Association's best recommendation for a dementia specialist who did extensive neurological tests and CAT scans and found that he had the beginning of multi-infarct vascular dementia and that he'd had numerous tiny strokes. They also thought that he had a possible secondary Alzheimer's.
Once I found doctors who understood the complexity of his brain chemistry, we were able to manage it with medications for the dementia (Aricept® and later Exelon®), aggression (Risperdal®), and depression (Zoloft®).
After much experimentation with combinations and dosages, the brain chemistry was properly balanced, without having to zombie him out.