It's a fair point Platapus, and terrorist or no terrorist the guy is a homicidal nutjob and should rot in a supermax for the rest of his natural (I say this rather than the needle since the punishment is longer lasting, rather than a quick and relatively painless death).
It is important though that we don't (and when I say we, I don't just mean people here, but everywhere) use mental illness as an excuse for these sorts of actions, or indeed come to associate mental illness with radical actions just as some associate Islam with terrorism.
It is important to help people with mental illness, just as it is important to help people avoid Islamic extremism, and so on. Hopefully in that way we will help to reduce the number of domestic terrorist incidents.
Is that me with an agenda? Perhaps, but it's an agenda to try to
stop more shootings like this from happening.