I’m sorry he lost his daughter but I despise parents who use their dead children as political props. If someone lost two children could they tell him he doesn’t know what a ruined life is?
His daughter's life was taken, and hence "ruined" but that Parkland father needs to realize that many other fathers and mothers have lost sons and daughters. He isn't unique in his situation. He is however wrong to try to leverage that tragedy for political purposes, where his goal is to remove the rights of his fellow citizens to defend themselves, their daughters and sons, and other people and their daughters and sons.
He should go to Washington DC and read the names on the wall of the brave young Americans who gave their lives trying to save other people from tyranny. And then think about their families, wives, and children.
And then he should do something to actually protect children - like campaign against the weak, ineffective security provided by the local law enforcement community.