As an outsider (I live in Australia) I find it amusing (and slightly scary) that removal of an individual's rights are automatically assumed to be evil.
In Australia, most people *don't* have the freedom to carry hand-guns (or crossbows or semi-automatic assault rifles) and mass killings in Australia are vary rare (only one that I can think of in the last 20 years).
What we have is freedom *from* mass killings. I'm happy to give up my freedom to carry deadly weapons if it means that most other people also don't have deadly weapons most of the time.
At the end of the day, the ultimate individual freedom is to be able to absolutely anything you want, absolutely any time you want to, including killing anyone you want whenever you feel like it. We deny people that level of individual freedom to protect the freedom of society as a whole to get on with their lives in (relative) safety.
And if someone goes mental in Australia, 99% of the time they go mental with fists or maybe a knife. If we can't stop all murderous psychopaths, I'd far rather have a murderous psychopath with a knife or two in my country than one with several semi-automatics.