So, who is responsible for giving an intern - likely not even strictly under an employment contact with the company - access at that level. And who, in turn is responsible for failing in their oversight duty of this situation? And who in turn is responsible for a the department that this fell under where such oversight duty failures are possible? And so on. Before long, you're back at the CEO, but that time the question will stick.

As a CEO you've got nobody to blame after your first 90 days of employment.