I would be highly suspect of anything in that article. For example, how did they get their hands on a confidential police document that appears to contain case numbers and personally identifiable perpetrator information? That in itself is an excellent reason why the ATF is and should continue to be prohibited from maintaining computerized firearms transaction records. Can you imagine the damage done to individual firearms owners if that database ever got hacked, and crooks, crackpots, and the media were to gain access to the information? It's already happened to numerous government databases; I have credit watches in place as a result.
The article also fails to mention the elephant in the room: Criminals aren't going to purchase guns through legal channels that leave a paper trail. The San Bernadino killers used straw purchases, most just steal them or buy them off the black market. And someone intent on commuting a crime isn't going to let one more law related to firearms stop them. These are just some of the reasons firearms registration doesn't work, and the even if the article's repeated cries for requiring all firearms purchases to be documented were to be heeded, criminals will still get their guns through undocumented channels.