~snip~
However, when the mentally unstable person had no intention of disturbing the people who were also gambling at the casino, the officers also didn't mind. They just assumed he was among the many gamblers who wanted to gamble. The officer allowed the person to gamble, and I think before the officer allowed the person to enter the casino, the officer must have asked his superiors first. Perhaps that's why the officers allowed the person to continue gambling after he finished his activities, especially since all this time, the person only came to gamble and left the casino after he finished gambling. And it wasn't a threat to the casino because they didn't see anything suspicious about the person while he was gambling at the casino. But if the person looks suspicious and has different intentions than before, the officers will interrogate him and take him to another room or even remove him from the casino and will not allow the person to return to the casino.
People who are mentally unstable will never bother anyone anywhere when they are all friendly with them and someone who is mentally unstable will only commit an act of violence or something else when their emotions escalate.
Moreover, there are only one or two people who experience mental disorders or are mentally unstable due to depression who engage in gambling activities.
All of this is also because from the beginning or for long time he was gambler and it would be very impossible if people like this stayed longer in the casino because they would not feel comfortable in crowded places.
I sure that if he hadn't gambled often at the casino in the first place then it would be impossible for the casino staff to let him in, just as the OP said that the casino staff said that the person was regular customer there who always gambled.
From what happened, it seemed like he had come into the casino just to bet and then left the casino and it seemed like there had never been any problems.
I sure something similar would happen in any casino when there are the same people in the casino environment.