Mental health provisions only make sense if theres a checks and balances system to ensure they are working. Consider this.
Unless individuals who are unfit to possess/carry firearms are actually identified, the reality is... theres nothing going to stop them from doing that. While laws don't prevent crime or even prevent evildoers from enacting their plans of violence, the very least the mental health system can do is identify those who are unfit to drive a vehicle, possess a firearm, etc, even if they aren't willing to commit that individual to a long term care facility. Do you want someone who's having violent thoughts driving a hazardous materials tanker daily? Do you want that person to be able to walk into a store and go purchase tons of ammunition and firearms? While I agree theres a fine balance between determining who should possess a firearm and not violating the rights of society at large, everyone can agree that these individuals did not develop their deep seated mental health issues overnight. One could also agree, that if the military is willing to pull an individual who is mentally unfit for duty from the ranks and to prevent them from possessing a weapon until they receive treatment, then surely law enforcement, lawmakers, and mental health workers can work on creating a system that identifies, treats, and makes sure that those who are unfit to possess weapons are not able to do so, to assist in preventing further acts of violence.
Maybe gun store owners should be required to go to training to identify individuals who are possible need of mental assistance to prevent future acts. For example, a firearms store owner probably shouldn't sell a gun to somoene who has cuts up and down their arms in various stages of healing, and appears/talks like they are depressed. While most gun store owners have "common sense" there are others out there who worship the almighty dollar, and will sell to just about anyone with a clean background check, despite whats presented in front of them.
A plan must be created and enacted to at least prevent those with serious mental illness from possessing a firearm. Thats simply a reality. One that balances the rights of the citizens and gun owners, to those who shouldn't have firearms. If society continues to do nothing, it feeds into the argument that these people "LEGITIMATELY" possessed and carried the gun when they committed acts of violence. This is how the far left lumps gun owners in with the crazies, because they say "See, you push to ensure everyone has access to a firearm, and now look with the mentally ill guy or violent criminal went and did!" The whole "I told you so" mentality catches momentum and its downhill from there.
Lastly, a concealed carry system needs to be worked into play in these states where these events are occurring to give citizens the means and right to defend themselves. These dirtbags pick gun free zones to carry out their evil plans because they know that theres little to no chance of them being stopped. Military bases, hospitals, nursing homes, daycares, shopping malls with "No guns allowed" signs all have become safe havens for criminals and crazies who intend to do bad things in a victim rich environment. If no one is allowed to carry a firearm, and the facility cannot be staffed with the proper amount of security personnel, who will put a stop to these events when they take place? The reality is no one. There isn't a big lawsuit against Malls of America for banning guns from their mall and failing to provide proper security staff who are armed to deal with the threats that they face. Nobody sues police departments for maintaining poor staffing levels that contributes to high death/casualty rates in violent incidents like these. Police aren't required to take action when your life is on the line, per Warren Vs. DC. Its up to the citizen to provide their own means of self defense. Thats what this boils down to.