Heckler? I think what was said needs to be figgered-out. I have cheap ear-buds hear at work.
Sounded like someone said "you know it's so" just prior to him saying thank you.
Don't have cheap earbuds however my ears do not work as well now as they did 40 years ago and listening to sound on speaker from laptop.
Same speech. Mentions Watergate, “How corrupt do you have to be to get kicked off the Watergate panel?”