The gun store just handled the transfers with little sales interactions. If they had a really bad impression they could have said no, but obviously didn’t happen.
Mentally deranged people are often very charming and easy to get along with. One of my former bosses was one of those guys. Nobody at work would/could find anything “bad” to say about him. One day he didn’t show up to work; he was in jail for beating his wife and kid.