This much is true. If that kid didn't have access to those guns, these killings might never have happened. That's not a federal gun control issue - that's a parenting issue. The responsibilities around gun access is the lesson here. If you want to look at that lesson from a political lens, it's a lesson for the liberty-loving 2nd Amendment supporters. Gun access should be made a more important topic as part of the "respect of guns" responsibility that all gun owners have. These are implements of war.
The only solution to this problem is impressing upon individual gun owners the tragic threats that unsecured weapons invite. Obviously people should inherently know this, but just as in everything when dealing with (training) people, repetition, repetition, repetition.
I hope that organizations like the NRA and the GOA take it upon themselves to use this tragedy as a platform for raising awareness about the issue of responsibilities of owners where gun access is concerned.