Quote from Lucrum:
It's none of their business AND most registration schemes are a prelude to confiscation.
If there is no national database and every gun purchase does not require background check, these tragedies will repeat over and over since too many loonies can easily buy guns. These same loonies, most probably know nothing about black market, and thus would not be able to acquire weapons there.
Background check and registration will not solve the issue completely, but it is a step in a right direction. Deadly object like guns need to have strong regulations.