The US is an outlier in how many guns we own, with about 1/3 of American adults owning guns, and we are also an extreme outlier in mass shootings unless you compare us to places that lack rule of law. How many more people need guns before that mass shooting number goes down to 0, do you think?
Given your link, I'd say every shooting where the bad guy didn't get shot is evidence in the opposite direction? Seems to me there's more of those than your 11 examples.
Now, how about your evidence?