Sooooooo... let me see if I'm following your thinking. Having guns is good because it reduced the amount of killings by someone who killed people... with a gun?! Great logic you got going on there.
Here in Canada we also have mentally ill people aswell, just none of them have mass murdered anyone, ie, Vegas and Texas. So your anti gun control argument is moot.
SAN ANTONIO SHOOTER WAS STOPPED BY A RESIDENT WHO OWNED A GUN AND CONFRONTED HIM! HOW MANY LIVES DID THIS PERSON SAVE?? YOUR GUN CONTROL ARGUMENT IS MOOT!