katherine herridge has that story. >> reporter: brand eagleson was 15 years old when his father bruce killed in the world trade center south tower. >> that's my dad. >> reporter: eagleson is now leading a group of 9/11 families battling their own government to release still secret fbi files from the case. >> it's a ten-year long investigation that specifically investigated the role that the kingdom of saudi arabia played in supporting the hijackers. >> reporter: the case code named operation encore centered on the two hijackers that lived in san diego and who assisted them. >> is that the first in san diego? >> this is it here. >> reporter: danny gonzalez was an fbi agent who worked on operation encore. he showed us the neighborhood the hijackers lived in. this is his first television interview about the case. >> it's 19 hijackers cannot commit 3,000 mass murders by themselves. >> reporter: based on what you found, do you believe there was a domestic support network for the hijackers? >> obviously. >> reporter: no question? >> i can't comment on it, but you don't have to be an fbi age