mucks hand but says call, what happens here?

[DMC0627]

Tourney, one guy goes all in, another guy said call but pitched his cards in the muck at exactly the same time. He obv meant to say fold. Argument ensued, floor was called. Floor came over, bottom line dealer didn't hear the call, although several others did, so floor decided it was a muck. The guy who said call said either way, he mucked his cards so that action would prevail. Others said verbal was binding. Yet others said whatever took place first would stand. I know there has to be a rule, but would like to know what it is. Info appreciated.