Probably to understand motive, and check for potential involvement of others.
And whilst they have a metric shit-ton of spying capabilities on US civilians, those are not really intended to avoid crime. (Maybe the shift of perception of what is terrorism might change that, though)
And whilst they have a metric shit-ton of spying capabilities on US civilians, those are not really intended to avoid crime. (Maybe the shift of perception of what is terrorism might change that, though)