As per the editor's box, "A Minute Alone".

The fact that Zoey and her folks were anticipating just having to put George's zombified body down, they just tossed him in a casket-- I'm betting they remove and reuse them. It's why he was buried wearing the clothes he was wearing instead of a suit.

Remember, Zoey's family covered all the costs of the funeral so the family and friends would have less chances to uncover the fact there was a ticking zombie bomb in the box.