Currently many are on the streets, oftentimes self medicating with street drugs, or imprisoned for various criminal offenses. Neither of which leads to a normal life. Your’re correct that their behavior just continues. I worked with a woman who had a son with bi-polar....serious violent behavior. Once he was of age the parents no longer could have him committed....needless saying he was in one criminal event after another. Ultimately he shot a cab driver dead and then surrounded the police shot him as well. It was a bitter sweet ending because had his parents been able to have him institutionalized these events would not have occurred.
That example you gave is so tragic for all concerned. Such people need professional help, and the average person simply cannot provide it. Surely a trained therapist can tell if a person is justly being pointed out as abnormal, so there shouldn’t be a legal reason to let that person roam the streets. San Francisco would be a good place to start picking up people and sorting them out for appropriate treatment since there are so many people on the streets with an array of obvious problems.
I saw a video on a homeless encampment in San Jose known for inhabitants on drugs. Authorities cleaned them out and started having them treated. One former homeless resident there said he now has an apartment and a job. He was very happy and said that many people were saved that day. Treatment is a good thing, not evil.