Yes, you can reduce the probability a little bit with regulation, education, preventive treatment for the mentally ill and such, but not enough. There are far too many guns already out there.
Moreover, there is nothing Congress is going to do about it. Didn't do SHIT when Gabby Giffords — one of their own — was shot, and it won't do anything for lesser mortals.
So what does Obama do? Remember him, Mr. Gun Control "using existing laws", who did nothing for his first term, except allow guns in National Parks, 'coz you know, compromise!
So the weasel delivers a speech (teleprompter), visits someone in the hospital (photo-op), and then this gem:
"We have to understand that when a child opens fire on another child, there's a hole in that child's heart that government can't fill, we should leave no stone unturned and recognize that we have no greater mission that keeping our young people safe."
That is after he said "[Such regulations] shouldn't be controversial. They should be common sense."
Well, fuck you too, Obama! Fuck you, and the common sense you rode in on!