The public may never know what motivated a 24-year-old Chattanooga man to kill four Marines and a sailor in an attack on Chattanooga's U.S. Naval and Marine Reserve Center last July.
Investigators have said Muhammad Youssef Abdulazeez was a homegrown violent extremist but have not offered more details about what motivated the attack.
Speaking to reporters during a visit to Nashville's FBI office on Friday, FBI Director James Comey said the shooting is still under investigation.
Comey said he understands the public interest in the shooting, but he did not know whether there would ever be a public report on it. He said the way the agency investigates sometimes makes it is necessary to keep information secret.
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