Unfortunately, it seems to take multiple massacres before anyone is prepared to step in. This report from WNYT in Albany, New York, concerns a Bennington, Vermont schoolteacher who was taken into custody because of mental health concerns. To read the newspaper account, the AR-15 he had was part of the problem, but watching this series of YouTube videos by him gives me the distinct impression that the concerns were legitimate. It appears that at least two of his neighbors, one of them his doctor, were sufficiently concerned about his odd behavior to contact police. In some of those videos, he makes reference to his wife leaving with the kids, and obtaining a restraining order against him; in others he refers to having been a schoolteacher until last October, and apparently has some negative views of his former employer. As a general rule, school teachers do not lose their jobs in the middle of the semester without pretty good reason.
This man apparently went into a mental hospital voluntarily, and it is no longer voluntary. This used to be the way we did things in America, before random acts of mass murder became something that we were just used to: neighbors looking out for neighbors, not only because of concerns about murder, but concerns about suicide.