Of course it doesn't make it Ok, it just makes a law banning something not actually that useful (as a method of prevention) when it comes to people who are willing to break the law.
Guns are banned in this country. If a ban on guns can't prevent gun crime in this country, it would never stand a chance in the US.
Gun crime saw 6,694 recorded offences in the 12 months ending September 2017, and we have some of the strictest gun laws in the world...
I don't get it, would you have preferred the school resource officer to have been prohibited from carrying a firearm?
Surely then the gunman would have been able to kill countless people before he was stopped, instead he was the only fatality. Surely that's a good thing?