When you picture the man (or already incarnate spirit) giving the command, it would be not be a yelling, but earnest insisting speech, only the closest would hear it, not 500 if they were present. It is said he appeared to 500 brothers, not that he had a "service meeting" Christian living portion with families gathering.
While we are in wt fantasy land: May be the 500 were the fellow revived ones that had come out of the graves and entered Jerusalem, now eager to learn what caused their unexpected new, temporary lease on life?