updated 03/24/2014 AT 10:00 PM ET
•originally published 03/24/2014 AT 11:15 PM ET
“That’s what you gotta do to get on the Letterman show,” retorted the actor, 42, whose character Will Gardner met an untimely demise on Sunday’s episode of the CBS hit.
Jokes aside, Charles’s departure from the series has been months in the making. After he chose not to renew his contract, Charles and showrunners Michelle and Robert King began planning Gardner’s memorable (and bloody) exit.
“It’s been one of the greatest gigs for me in my entire career but at the end of last year, my contract was up and I was ready to move on,” Charles explains.
“It is tough to leave stability and structure, but it was great for the show and also a really proper goodbye to the character.”
He adds, “We’ve been able to keep it a secret for an entire year!”