There are currently more guns than people in the United States. The last estimate in 2015 put the number at around 357 million guns.
Time to do a little math.
Firstly, since there are mass shootings involved, my next premise is false, but it should still illustrate the point well.
There were 53,270 gun related incidents in the United States in 2015 (Source: http://www.gunviolencearchive.org/past-tolls). Lets assume then that in each incident, a different gun was used. Again, I realize that the number of guns used in those incidents is most likely lower. Still, using that figure, that means that roughly 0.00015% (0.00014921568 rounded) of guns in America are being used for violent purposes.
The way the media reports these things, and the way people react to it, one would think that all we do in America is shoot each other - and that is simply not true. Most gun owners are responsible, law abiding citizens - and taking their guns away is not the solution. Particularly since, with today's technology, guns can be made at home with relative ease.