The percentage of violent schizophrenics is lower than in alcoholism. There isn't really a link between violence and schizophrenia.
There is other disorders that are a lot more violent, I don't understand why schizophrenics always get a bad name and are portrayed bad in the media or whatever. Just because there is some violent schizophrenics doesn't mean they all are. Allot of schizophrenics are almost "normal" you wouldn't even know they were schizophrenic, I think people get mixed up with psychosis, psychopathy and even MPD/DID sometimes, mostly because of that movie.
As i'm sure you know, "Schizophrenia" covers a broad spectrum of different deseases (you work in the Psych field perhabs? you seem more informed than most), from the very mildest kind called "Schizotypal Personality Disorder" which is practically more an annoyance to the patient than a desease, to the very extremes, which is "Paranoid Schizophrenia", most Schizophrenics are harmless, and will never spend a single day in a psych ward, because their symptoms are no cause for alarm, most don't even need medication, but the exception is the last group, the Paranoids, thease are the ones who have psychotic eppisodes, who hear voices and have hallucinations, they do need meds to live a normal life (and sadly, anti-psychotic meds have some terrible side effects, causing many to stop taking them), and some, even though it's rare, can become very dangerous durring their psychotic eppisodes (not because they are bad people, but durring psychosis they are nolonger in the same world the rest of us are, in their world, people might not even look like people, they could look like Demonic creatures, some of them do harm thinking they are defending themselves), and they often wont even remember it after the eppisode is over.
Now this guy says he heard voices telling him to kill people, that definately suggests he is a Paranoid-Schizophrenic (one with a very unpleasant past), and also the potentially dangerous kind, and if he had a full blown psychosis, then yeah, that could be the cause right there.
It's rare, certainly, but some Paranoid-Schizophrenics can be a danger to themselves and others because of their illness.
Try to think about it from a schizophrenic's perspective, would you like everyone to just presume that you were some murderous violent psychopath just because you had schizophrenia?
Unfortunately this is very true, most people will emediately think of the very worst cases of Paranoid-Schizophrenia, or even get it confused with Multiple-Personality-Disorder, when they hear the word "Schizophrenia", but the truth is that this is a rare illness, most Schizo's have a much milder form of Schizophrenia, and even the Paranoids are rarely dangerous, Schizophrenia is no reason to fear people.