His son, Jason VanBorssum, tells the Los Angeles Times (http://bit.ly/1uH8hbv ) Marshall died of esophageal cancer on April 26 at a Santa Monica hospital.
Marshall began voicing the Kellogg's Frosted Flakes mascot in 1999, filling in for the original actor, Thurl Ravenscroft.
Marshall got his first full-time radio job at the age of 14 in Phoenix. He had a prematurely deep voice and lied about his age. His career included radio newsman, rock 'n' roll disc jockey, sports broadcaster and wrestling ring interviewer.
Information from: Los Angeles Times, http://www.latimes.com