Very true Jersey Girl, with manic depression, their impulses may not as controlled, but in the case of Raven, besides the mania, there is such a hightened visions of grandure with him, that leads me to suspect, that he also has some sociopathic tendancies. You can have more than one form of a personality disorder.
Mania causes irritability, impulsivity, and imparied judgment. It could then lead to murder, but I do believe that the murder of Janet was more thought out, whether it started that day, or a day or two previously.