It’s easy to diagnose these in hindsight, but there are thousands of people who live with mental illness that never do something like this and function well. They have the same civil liberties that you and I do.
Sadly, our mental health system is mostly dependent on insurance coverage and pharmaceuticals. Pinky promise that you will take these pills that make you feel odd when nobody is around.
Mental illness rarely has an easy solution, but it always invokes strong opinions after the fact. Just throwing that out there. There are many people who struggle with mental health that do not have strong family units or a support network and something like this is extremely rare and if 1000 people are schizophrenic with violent tendencies and only one of them acts out like this in a horrific manner do we institutionalize the other 999?
I don’t any specifics about this case so this is just a general point to consider.
Actually, they don't. For instance, if you're mentally incompetent, you cannot enter into a legally binding contract. You cannot serve on a jury, or as a witness in a trial, not even your own. So, they are already subject to some restrictions.
I agree this is a complicated subject. But, at the end of the day, I think there are some diagnosis and medications that should be disqualifying for buying or possessing firearms. Paranoid schizophrenia is just such a diagnosis. People who are hallucinating, even if they're plainly non-violent, probably shouldn't be handling weapons
I also agree that there are a lot of crazy people who have little or no support system and that's a huge problem. But, a surprising number of these spree-shooters do have families, middle-class and even upper-middle class families. Semi-automatic rifles aren't cheap. These aren't homeless nutters walking into 'gun free zones' shooting up the place. These are oftentimes people of some means. The Colorado movie theater shooter's mom was a psych nurse and his dad had a really good job, IIRC.
Ultimately, we either take some measured, circumspect steps to get a better handle on the mentally impaired's access to firearms, or we're all going to see restrictions on our own civil liberties.