If you don't agree that he's evil, I don't really care. If you want to debate the meaning or interpretation of what is "evil", then find some discussion board on philosophy and have at it. He's evil in my book.
I think you are confusing evil with tragic and horrifying.
There is no doubt his actions were the latter. There is considerable doubt he had the capacity to control his actions. If that is the case, it is very hard for me to call him evil. To me he would appear to be one more tragic victim. Unless, of course, your religion doesn't believe in mental illness and thinks he was possessed by a demon - I guess that
would make him evil, but still not capable of making choices and controlling his responses.
It is not an academic distinction. If you are going to try to prevent future actions you need to be aware of what causes them and what remedies might work. Mentally ill people who can't control themselves fully cannot be dealt with the same way you would with a sane but criminal person out for revenge. (On the one hand, fear of punishment means nothing if you can't stop yourself; on the other hand for some mentally ill medication is effective, but it doesn't do anything for the criminal.)
I was attacked by a mental patient once. Well, quite a lot of times actually, but let me tell one relevant story. This guy was organic brain syndrome, damage from auto accidents. He had a whole range of symptoms as a result, but among them feeling frustrated and "wrong" all the time, and given to rages he couldn't control. He was in numerous fights when on the street, and when hospitalized had committed numerous unprovoked attacks and injured a number of nursing staff. He was an averaged sized guy, about 5'10" and 180 pounds, or 1.8 meters 85 kg for you metric types. I walked by one day at the wrong moment, paying insufficient attention, and he jumped out of his chair and punched me in the head. Now, he had nothing against me personally; that day the combination of his internal state and a medication change had left him a ticking bomb.
His punch spun me around so I wasn't looking at him. The adrenaline dump shrunk my vision to a tunnel, and I actually never did see him again during the incident. I stumbled back across the room, getting punched each time I stepped back but not knowing where he was. After 5 or 6 times it occurred to me to step forward instead of back. Found him, subdued him. A couple hours in seclusion and he was back in control and out on the ward again.
Blame him? No, I couldn't. He was difficult and unlikable even when not violent. But when you understand him a little you can't call him evil. In the wrong circumstances his actions could produce results as bad as in Virginia. Once you've dismissed it as evil you stop thinking about it and the chance of coming up with rational ways of dealing with it end.