The first thing I would do is attempt to weed out witnesses who are either glory hounds fabricating a description so they can be in on the action, or RINGERS which the terrorists have sent in to give fake descriptions to confuse the police.
I would start asking witnesses if they would take a polygraph. That would weed out a few, IMHO.
On the "safe house" idea put forward in World Net Daily's article, here's an extract from Al Qa'eda's training manual:
Prior to the operation, apartments should be prepared to hide the brothers participating in it. These apartments should not be known except to the commander and his soldiers.
This is from a discussion specifically dealing with assassination.