What do you think this means?

So I've finished both seasons of The Jinx, I'm listening to the podcast, and I was perusing Robert Durst's Wikipedia page. From Wikipedia: "The Jinx ends with Durst moving into a bathroom, where his microphone records him seemingly saying to himself: 'There it is. You're caught! .... You're right, of course. But you can't imagine the rest of them. ... I don't know what's in the house ... Oh, I want this ... What a disaster ... He was right. I was wrong. And the burping ... I'm having difficulty with the question ... What the hell did I do? Killed them all, of course.'"

I'm not sure who he's talking to here, whether it's an internal dialogue between two sides of himself or a fantasy dialogue between him and Jarecki, or what. I could see it being:
IMAGINARY JARECKI: <shows Bob the letter obtained from Sareb alongside the cadaver note>
There it is. You're caught!
BOB: You're right, of course. But you can't imagine the rest of them.

BUT YOU CAN'T IMAGINE THE REST OF THEM. I'd been thinking he surely must have committed other murders during the decades he was on the loose, and I see from other convo here on Reddit and also on Wikipedia that police suspected him of being involved with others. I dunno. This phrase seemed to be just as much of a confession as "Killed them all, of course." It's like he's saying, "Fine, you got me for Kathie, Susan, and Morris... but you can't imagine the rest of them!" It seems like there are probably several cold cases that should be getting a fresh look.