Unless the controller was already here. And instructed to act on his own initiative under certain circumstances...
The more thought we're applying to the situation, the more likely it seems that many of the risks can be suppressed.
But I just don't think we're necessarily going to be able to eliminate every single one of them. It's conceivable, but we'd best not plan on it, certainly.
All he has to do is hand over his germs to the terrorists
(in some third country)
and they will do the work for him, lots of fun for years to come.