Can the Self Be Saved?
Clearly Cho was struggling with mental illness, so right away he's not responsible in the way a sane individual would be, whatever your worldview is. But from a naturalistic perspective, sane individuals have coherent personalities and behavioral repertoires which determine their choices, even if these in turn are (likely) fully determined phenomena (and even if they weren’t determined that wouldn’t give us more responsibility, as David Hume saw long ago). We have a strong, internal, emergent experience of being a self, and strong hard-wired emotional responses that track moral rights and wrongs. And we must as a practical matter continue to hold each other responsible (as compassionately and non-punitively as possible) in order to make each other into good citizens. So Brooks can be reassured that yes, we can still legitimately explain actions as the outcome of choosing selves (as a practical matter we’re forced to explain behavior at the personal level of conscious intentions, not the sub-personal level of neurons, etc.) and we can and must continue to talk of moral responsibility. The upshot is that human agents and morality don’t disappear when naturalized. This is the burden of chapters 3 and 5 of Encountering Naturalism.
But there’s one huge difference under naturalism: the self is not a "moral levitator" as philosopher Daniel Dennett so nicely put it. On a naturalistic understanding, we see that the self is fully a function of bio-social processes, and that therefore we can't demonize wrong-doers the way we could on the old, soul-based, self-caused view. Plus we'll pay more attention to the actual causes of horrific acts, both in mental health and gun-control policy. If people see that we can have viable notions of personhood and moral responsibility under naturalism, and that these lead us to act more compassionately and effectively, they’ll be far more likely to accept it.