Maybe he did and maybe he didn't; but obviously the FBI isn't the only agency which thinks it's possible.
If it's possible, then we have to assign probability and react accordingly. I'm no expurt, but in my opinion some of the posts here ring of complacency or even denial.
There seems to be an attitude of "no one with any brains would design a system with such vulnerabilities." Unfortunately the historical record indicates otherwise.
A few well known examples:
Apollo 1
Challenger
Columbia
Pinto
Drive On - Drive Off ferry boats
HMS Sheffield
And many others....
"It appears that there are enormous differences of opinion as to the probability of a failure with loss of vehicle and of human life. The estimates range from roughly 1 in 100 to 1 in 100,000. The higher figures come from the working engineers, and the very low figures from management. What are the causes and consequences of this lack of agreement? Since 1 part in 100,000 would imply that one could put a Shuttle up each day for 300 years expecting to lose only one, we could properly ask "What is the cause of management's fantastic faith in the machinery? .. It would appear that, for whatever purpose, be it for internal or external consumption, the management of NASA exaggerates the reliability of its product, to the point of fantasy." - R. Feynman