I read 5 different versions of this article, including the one posted on Stanford's webpage.
They use words like "linked", "associated with", and "connected" to say in a round-about way that the increase in right to carry states somehow caused numerical increases in gun-related violence.
Correlation does not equal causation! If the percentage of female babies born in 10 years coincides with a similar increase in cancer patients, are we to assume the female births are causing cancer?
If they can't do any better than drawing conclusions from pure statistics, then the study is useless. They need to actually find the CAUSES of the increased violence, not try to link it with people being permitted to carry firearms.
I once did a study to find the best place to eat and lose weight so I could drop a few pounds and still eat out.
I discovered you should never, ever eat at a place with a salad bar!
Every nice, big salad bar I observed was always surrounded by obese people! Thus, I concluded salad bars must be making people fat!!