Looking into this I found Mr. Robert Mueller’s comments on MAJ Hasan, the FBI did not drop the ball. https://www.motherjones.com/politics/2013/08/nidal-hasan-anwar-awlaki-emails-fbi-fort-hood/
The most recent MAJ Hasan news (2017), he is one of 6 at Fort Leavenworth on death row, no news on how this hunger strike went. https://www.armytimes.com/2017/04/04/fort-hood-shooter-goes-on-hunger-strike/
Death row in the military means the case is reviewed by various military courts and likely the US Supreme Court and the President will have to sign the death warrant. So let’s get it done!