Why do stories like this get such banner headlines, when stories like this do not?

Story 1 is a clear tale of negligent parenting.  The weapon did not jump up and jump into the child's arms.  The weapon could have been a butcher knife or a lawn dart.  Still, any "responsible" firearms owner knows that your weapon should only be in one of three places; on your person, in your hand, or in the safe.  All mean under your control.  And if it is the child's weapon, then the parent needs to be in control of it, just as they are with other potentially harmful items in the child's environment (again, is Johnny playing with the steak knives?).  BTW, a father recently backed over his daughter with a lawn mower and cut off her feet - no charges yet and no plan to outlaw lawn mowers that I have seen.  How do we define negligence anyway?  Well, surprise world - terrible things happen when one makes terrible mistakes and acts negligently in some way.  Often those things happen to children when parents are inattentive.  This is not meant to belittle such tragedies; it is meant to place them into proper context.

Story 2 is a clear tale of responsible gun ownership and highlights the fact that not all gun ownership is evil.  Consider what would have happened if this armed citizen had not been in that area, leaving a knife-wielding assailant to hack away at unprepared and apparently unarmed and unprotected victims.  Also note, as is often said (at least in some circles); "When seconds count, the police are minutes away."  How much more damage could have been done here in a couple more minutes [BTW, we're waiting again for the call to do background checks for knife purchases - if the store had done this, think of the trauma that could have been avoided].  This is not meant to diminish or denigrate the role of the police - it is clear that their job is not to prevent crime and the notion of to serve and "protect" is misguided.  They cannot be in all places at all times.  Hence, the need to guard the right to self-defense (self-protection).

Yes, my question above was obviously rhetorical; we know full well why one gets the coverage and the other does not.  Because news is not really news, news is agenda driven.  Top billing goes to the cause the news outlet supports.