Whenever there is a mass killing of innocents by some deranged person, America tries to search its soul as to why it happened.
In the case of Dylann Roof, it appears that all the signs were there. Many things in his life were pointing to what ultimately culminated in the senseless slaughter of 9 people at worship. So why were we unable to do anything about it? Because, in America, you can't involuntarily commit someone for mental illness unless they have already demonstrated that they are a danger to either themselves or others. Nor, can you imprison someone solely on the basis of what they say or how they dress or what symbols or tattoos they adorn themselves with. The courts have ruled that even the display of one of the most vile symbols, the swastika, is protected by free speech. For these reasons, Roof was free to roam the streets.
As far as the gun control issue, it probably wouldn't have stopped Dylann from doing what he did. Statistics have shown that 89% of the juveniles in our correctional systems owned a gun or guns at some point before prison. All of which were illegally obtained. Only 15% of inmates in our Federal prisons said they purchased guns legally. Also, we can't legislate a moron father who hands his mentally ill, druggy son, a weapon for his birthday. Stupidity in this country -- as bad as this was -- is still not a crime. Perhaps, however, we should consider finding adults guilty of associated murder charges when a gun, they knowingly give their child, is used in a murder.
Like it or not, there are more Charlestons in this country's future. Gun control or not. The weapon could have just as easily been a pressure cooker bomb and not a gun. Going all the way back to the killing of Abel by Cain, the kind of hate that was exhibited in that Charleston church has been and will always be with us. Jews, like Blacks, have been killed out of hatred. Christians are being slain by the hundreds by radical Muslims. Gays, too, especially by Muslims, have been the target of slaughter, and even Arabs slaughter each other because one might be a Sunni versus a Shiite.
I believe that the increase in the kind of Charleston-like crimes is because of the breakdown of the family unit. Too many single-parent families and the increasing rejection of religion. But, too, we are a country that has been desensitized to violence by violent video games, movies, and TV shows.
Committing a mentally ill adult is complex: http://www.usatoday.com/story/news/nation/2013/01/07/mental-illness-civil-commitment/1814301/
The Constitutional Protection of the Swastika: http://www.jstor.org/stable/1142331?seq=1#page_scan_tab_contents
The legal loophole that allowed Dylann Roof to get a gun: http://www.washingtonpost.com/blogs/govbeat/wp/2015/06/18/the-legal-loophole-that-allowed-dylann-roof-to-get-a-gun/
Charleston Massacre: Mental Illness Common Thread for Mass Shootings: http://www.newsweek.com/charleston-massacre-mental-illness-common-thread-mass-shootings-344789
Illegal Guns Statistics Overview: http://gun.laws.com/illegal-guns/illegal-guns-statistics