For me, firearms were normal. For hunting. For shooting competition. Even some school clubs for the latter.
Firearms were carried and used carefully like other dangerous tools.
Shooting people with them, though? Very not normal. If someone had told me as a kid that "if a shooting happens..." I'd have nodded and finished it with "render first aid," because someone made a mistake or had an accident and will need help.
But "Run and hide?" Augh, I hate this timeline.