Interesting subject, the UN did a study published in 2015 concerning privately owned guns across the nations, it reveals some interesting numbers. I regard the UN as a credible source.. sources are important and the reason I almost never "like" anything on social media, I may not be aware which people and organisations I randomly support by doing so, modern terms like "click-bait" comes to my mind when I read the OPīs linked article.
The UN study in PDF format here:
You can find a short article by The Guardian titled; "Gun homicides and gun ownership listed by country",
based on the data provided by above study here:
(copy/ paste the url-string in your browser)