Tom Selleck, a friend of screen legend Charlton Heston -- and his costar in the 1976 war drama "Midway" -- told CNN on Monday that he was caught unaware by Heston's announcement Friday that he is showing early signs of Alzheimer's disease. "His announcement was so typically Chuck -- he did it with grace and dignity and intelligence," Selleck, 57, told CNN's "Wolf Blitzer Reports." (CNN, like PEOPLE, is part of AOL Time Warner.) Selleck, who considers Heston, 77, a mentor, said that he phoned the "Ben-Hur" and "The 10 Commandments" star after the announcement of his medical condition was televised. (Heston's revelation came in a videotaped message that was played at a Beverly Hills press conference.) Recounted Selleck: "He said, 'I still got a lot of fight in me, and this isn't the end of the line.' And that's very much Chuck, too. He had a lot of humor Friday, and it was great to talk to him." As to whether the former "Magnum, P.I." star would be willing to succeed Heston as president of the National Rifle Association, of which Selleck is a vocal proponent and life member, Selleck told Blitzer he would serve if approached. Heston plans to serve to the end of his third term in April.