I did not know him personally, but I attended some of his speeches and was impressed by his editing and writing for the LP News. I was captivated by his melodious voice and friendly demeanor.
Here is a recent story about him.
https://www.libertarianism.org/articles/karl-hess-and-death-politics
The article doesn’t mention it, but it has been claimed in many places that he was the ghost writer for Barry Goldwater’s speech with the line “extremism in defense of liberty is no vice.”
https://www.niskanencenter.org/on-the-saying-that-extremism-in-defense-of-liberty-is-no-vice/
He ran as a Libertarian for Governor of West Virginia in 1992, shortly before his death. When asked by a reporter what his first act would be if elected, he quipped, “I will demand an immediate recount.”
https://en.wikipedia.org/wiki/Karl_Hess
Here is a 1981 documentary about him.