This kind of bovine excrement really pi55es me off. Was the 19 year old ever convicted of a felony crime or misdemeanor crime punishable by more than one year in jail? Was the 19 year old ever adjudicated mentally deficient by a court of law? Was the 19 year old ever convicted of misdemeanor domestic abuse? If not, then on what grounds should the 19 year old have been stripped of his constitutional rights by the FBI, by the NICS system, or by the FFL who sold him the rifle?
How many other "troubled" individuals should have their constitutional rights revoked in advance of any prohibiting behavior? Are we now the office of pre-crime? Are we now going to act on the concept of prior restraint - revoking rights or even jailing individuals because someone thinks that they might commit a future crime?
Yeah, this a-hole had serious issues, and local and state law enforcement and school officials had ample opportunity to respond appropriately to get this individual help or to charge him with a crime and remove him from society. But unless and until the individual is charged and convicted of a crime, there is little that the FBI or NICS could have done to strip him of his constitutional rights. Or yours.
You can flag people in that database without denying their right to buy a gun.