He attended Ithaca College and later studied political journalism at Georgetown University. He became the anchor for ABC's World News Now when he was twenty-nine years old.
He received the National Headliner Award for his news coverage during the September 11, 2001 attacks.
He was born to Ronald Muir and Pat Mills. He has one older sibling and two younger step-siblings.
He co-hosted 20/20 with Elizabeth Vargas.