The failure of the mental health system is a common thread through the Texas church and killings other killings that are in the headlines.
James Holmes, the Colorado theater killer, is perhaps the best example. He tried to contact his psychiatrist while his tenure in a graduate program was falling apart. Other examples are less clear-cut since we know less about their psychological care and treatment. Jared Lochner, who killed a bunch of people, had been expelled from Pima Community College. Adam Lanza's schooling in an affluent Newtown, Connecticut should have exposed him to mental health professionals.
In an incident strikingly similar to the Texas massacre, Esteban Santiago killed six people at Fort Lauderdale International Airport in January 2017. His downward spiral is detailed here, Fort Lauderdale shooter Esteban Santiago saw life falling apart
(link). The article details how "a tape of a January 2016 domestic violence court hearing after his arrest for fighting with his girlfriend, a prosecutor lays out the case, explaining he broke down the bathroom door at Peterson’s home, then hit her in the head."
Kelley, the murderer in Texas, had similar domestic violence problems. They both had troubled military service.
De-institutionalization was a well-intentioned program. It was supposed to convert inhumane and, for the patient ineffective confinement into treatment in the community. This April 2, 1972 article, which I remembered reading,
The Patients Can Walk Out At Any Time at Bronx State Mental Hospital (link) made the case for de-institutionalization. Unfortunately few were as motivated as Israel Zwerling, and most looked at the process as a way of saving money.
The mental health system is not doing a good job of keeping these people under control. While the status quo ante before mass de-institutionalization was inhumane to the patients, it did keep the country safe from the lunatics. Perhaps the balance needs to be tipped more in favor of the public than the lunatics.
We can work at improving the humanity, and where appropriate the therapeutic nature of these centers. But we were safer with these people locked up than out loose.