I mean correlation doesn't mean causation. Perhaps the very reason the bought a handgun is because they thought they had some threat or were involved in activity that would increase their likely hood of getting killed.
This study looks at the broader question of people who started living with handguns in the house, from a baseline of no handgun, so many of those victims are not people purchasing weapons themselves.
The absolute numbers are low (12 killings / 100,000 pop as opposed to 8 / 100,000 in the control group).
I don't think the article claimed causation but you can't determine causation from this type of study either. There's a possibility of the data being random, as well as causality going the other way, but it is hard to temporalize getting killed causing someone to start having a handgun in the home before that point. There's also a possible third unknown and causal association that is responsible for both the killing and the prior presence of the gun. That is a definite place to do research.
If we start with those numbers and a null hyp that both the control and the "experimental" group have a mean of 10, then the chance that of finding 4 or more extra killings than in the "experimental" group is about 21%. So even assuming no p-hacking, your p-value is meaningless.
The absolute numbers are low (12 killings / 100,000 pop as opposed to 8 / 100,000 in the control group).
I don't think the article claimed causation but you can't determine causation from this type of study either. There's a possibility of the data being random, as well as causality going the other way, but it is hard to temporalize getting killed causing someone to start having a handgun in the home before that point. There's also a possible third unknown and causal association that is responsible for both the killing and the prior presence of the gun. That is a definite place to do research.