What you have here is a young man coming to the realization that he has thrown his life away and is facing a living hell for the remainder of his time on earth.
When he was planning these atrocities, no doubt he had delusions of grandeur. Maybe he thought he was going to become some sort of cult hero. He might even have envisioned escaping the scene of his crimes, at least temporarily, and watching the news unfold on a motel TV as he planned to drift across the country and melt away into the landscape.
Instead, he was caught almost immediately and slammed into a jail cell where he has had the entire weekend in isolation to think about what he has done and what lies ahead of him.
This is not the look of an insane or drugged man. This is the look of a man who now realizes he has done something horrible and will never take another free breath again. He will be locked up in a prison cell the rest of his life and that's not even the worst of it. He will need to watch his back at all times as his fellow inmates will want to hurt or kill him at the first opportunity. He won't even be able to take a bite of prison food without wondering whether somebody spit or peed in it or worse (and you know they will).
In short, it's all downhill from here for this wretched human being. With the deeds done, there is nothing good to look forward to in this lifetime. Nothing. This is the look of a man who is staring into the abyss.
He would probably do OK in prison, if he hadn’t killed a six-year-old girl.
Totally agree. I saw horror in his eyes. That realization of “what have I done?”. Video games aren’t real life. Reality is knocking on his door. Playing the joker sounded like a good thing at the time for him when life was in disarray. World of Warcraft and role playing games might dominate one’s head and it can blur the lines of fact and fiction. Throw in a bit of developing mental illness and your take makes perfect sense.