The Glee alum recalled his reaction to the tragic news and how he turned to Naya Rivera.
"10 years ago today I was in London with Naya," he tweeted on July 13, the anniversary of Cory's passing. "We immediately met up after being woken up by the worst possible news. We spent the day partly in shock, partly laughing at our memories, partly crying at the impossibility of it all."
"What pisses me off," he said on the April 16 episode his and Jenna Ushkowitz's podcast And That's What You REALLY Missed, "is he was such a good actor and I don't think we necessarily told him that enough."
The 35-year-old's comments were prompted while he and Jenna were discussing the show's season one finale in which Cory's Finn Hudson kisses Lea Michele's Rachel Berry.
"This whole episode, I was just floored by Cory," Kevin continued. "So good. It's ridiculous."