I don’t know if schizophrenia would be the likeliest diagnosis. Schizophrenia is first a thought disorder — the “voices” a schizophrenic hears are disturbing and can reflect bad intentions, but they’re not very good at planning things, particularly over a long period of time (evidently, this guy was gathering material for his evil project months in advance).
Schizophrenia slows you down, especially if you start taking medications for it; when an acquaintance of mine started developing schizophrenia in graduate school, being in his presence made you feel like time had slowed down for him — it was very difficult for him to transition from one activity to another, and he would tend to settle by default into a pattern of aimless pacing. As the disease progresses, one’s inability to complete even simple activities of daily living (hygiene, getting to appointments) becomes increasingly pronounced.
In Holmes’s case I suspect a personality disorder combined with bipolar mood disorder: the guy had intelligence enough to stick with a sophisticated plan (no serious thought disorder) that showed extreme inability to empathize with other people (severe personality disorder), and shifted into a high-gear, maniacal flurry of activity after experiencing some emotional trigger (manic phase of bipolar disorder). Mentally ill, yes, but fully capable of understanding the immorality and criminality of his deeds.
there is a poster here who thinks he has Aspergers