You have a choice, he’s either lying, or he’s an idiot. You can’t “buy guns” over the internet from any type of dealer without having a check and PROBABLY having it pass through an FFL shop in your state if it’s interstate or in a state requiring a wait.
You could, of course, get in touch with someone on a forum and then meet them FTF and conduct a transaction, for which I find absolutely nothing wrong personally, but which in California would be illegal.
The mere fact that he brought this up publicly indicates some type of willingness to throw this out there to the advancement of someone’s agenda...
Who says he bought if from a dealer? Nobody is saying that. It could have been a private sale off Craigslist for all we know.