I've had some very close relationships with C levels at some big and medium companies. I've caught them lying in varying degrees more than once.
Sometimes though the job demands it. They're potentially not allowed to disclose something which leaves lying or saying nothing as the only other options. This works well until someone already knows the truth -- has their own source of information.
I didn't take offense, I just learned not to take what they said at face value. It's not a bad lesson in general. C level executives often learn to be ruthless, depending on the org, they can end up in real internal power struggles as well.