Very sad news. Met him last year at a comic con and he was very friendly, funny, and personable with fans. Seemed like a genuinely nice guy beyond his iconic TV roles. He was scheduled to be at a Connecticut comic con in August with Burt Ward and Lee Meriwether, so his health must have deteriorated unexpectedly.
Was really sad to see this news in my feed when I woke up. I'm a huge DC Comics fan and I love the Batman '66 series. Was so glad that it finally found its away onto to home video just a few years back.