Complex sentence: Reed died of a heart attack in Los Angeles, California, shortly before his 70th birthday; his final performance of Fred Flintstone was for the latter's cameo guest shot in an episode of Scooby's All-Star Laff-A-Lympics.
Split into simpler sentences: Reed died of a heart attack in Los Angeles, California. His final performance of Fred Flintstone was for the latter's cameo guest shot in an episode of Scooby's All-Star Laff-A-Lympics.