Is very simple. Exactly what are you proposing that would have prevented the shooting at Parkland? No dodges. You can't say 'well Dave, you can never be sure ...'. Nope. You have to say this is what we propose that, if it had been in place, would have prevented the shooting. It's easy.
For me, looking at guns as separate from the society we've built is like looking at air pollution as the world's main problem in 1944.
Also, my boys asked an interesting question. Has anyone older than a Baby Boomer ever been involved in a mass shooting in the modern era of mass shootings? I'm sure there have been, but I'd be interested to see the numbers. Mass shootings as we think didn't begin until the late 70s/early 80s. What happened then to change things? I think that's what they were aiming at with their question. Why did this all begin? It's not just guns.