Mr. Williams is a hulking Caucasian male with a brown buzzcut, and a five o'clock shadow.
A Pup Named Scooby-Doo
He retold his story on the news, about working late one night at the bank, and witnessing the Sludge Monster from the Earth's Core inside the vault, stealing the money. When the Scooby-Doo Detective Agency was on the trail of the Sludge Monster at the bank, only then when they found Mr. Williams, it made him a suspect. Given the rough appearance of Mr. Williams, as well as the temptation of being around large amounts of money, it made sense that he would try to rob the bank as the Sludge Monster. However, Mr. Williams was found innocent after the gang unmasked the monster as Mr. Buckston, and thanked the gang for exonerating him. (The Sludge Monster from the Earth's Core)