The trouble with excuses. . .

If there were 1) no NRA, 2) a perfect screening database for legal gun ownership, and 3) no high capacity gun magazine [and there actually wasn't one], the Parkland shooter would still have killed 17 people, or more if all his plans and gun had worked properly [it jammed].

The failures, the reasons he was not stopped, and those people are dead, are
1) Sheriff Israel and his "leadership,"
2) the school board,
3) the superintendent,
4) the federal government "Promise" program,
5) the officer who guarded the perimeter instead of going into the school,
6) the FBI,
7) security guard who hid.

No matter how much you want it to be so, the anti-gun people can't blame the President, the NRA, the shooter's age, or even legal rifles. The result would have been the same if H. Clinton were the president. The difference would have been in the news media coverage and the social media memes whipping up the hate and hysteria.