How's it inconvenient? If I lived in the US I'd probably keep a firearm in my house too while the gun laws are so ridiculous. I'd much prefer to not have to!
What has this and wanting sensible gun control enacted got to do with eachother? She fired 1 round, you don't need an ar15 to have done that.
What is inconvenient is going shopping when some loon snaps and goes on a spree of their own with their legally owned weapon.
In what circumstances would you not have to? Criminals don't obey the law, they're already committing crimes by shooting people and/or breaking into houses, the only people gun laws affect are people who wouldn't commit those crimes anyway.
Yes it's extremely tragic when someone decides to shoot up a place, but that seems to be more of a cultural thing that needs addressing. It seems to be partly mental health, people feeling isolated, disenfranchised from society in general - these are things that need addressing. It's the same as people who decide to commit any act of random violence, there are underlying problems to begin with, you don't solve them by attacking tools that law abiding citizens use. When people were using vans to drive into large groups of people, no one blamed the van.