https://www.theatlantic.com/politics/archive/2017/06/right-to-carry-gun-violence/531297/
http://www.dailywire.com/news/8255/report-concealed-carry-permit-holders-are-most-law-aaron-bandler#exit-modal
https://www.washingtontimes.com/news/2015/jul/14/murder-rates-drop-as-concealed-carry-permits-soar-/
所以下次不负责地发帖之前最好先do a little research