I agree with you that the last murder should have been looked at closer. If the FBI had reasonable suspicion that he was a possible known terrorist why did they take him off their watch. 
If the no fly/no buy list was done in such a way that  rights were not infringed and equal justice was granted then I could agree to that. The rights of the accused facing the accuser in a court of law before a jury of their peers. 
None of us have all the answers. We can only voice our opinions in search of a possible solution. 
P.S. I am not a member of the NRA or any other gun organization but I strongly believe in the 2A.