Did just a little bit of digging on this guy because his entire claim sounds bogus from the get one.
First of all, anyone with military and/or law enforcement experience would know the difference in an automatic weapon and a semi-automatic weapon. They would not confuse the two completely different terms.
Second, he claims he saw a girl with her face blown off. A shotgun could do that and a large caliber rifle round might, but a .223/5.56mm round would not short of standing over the body and just unloading a magazine into the face after the person was dead. The shooter did not do that.
His story sounds just like David Hogg's. He raced to the scene after the fact and is suddenly the face of the anti-gun movement. Only difference is he claims he owns guns (if he does, probably a double barrel shotgun or some old pistol) and supports the 2nd Amendment, but of course all his talking points come from the Democrat playbook.
Lastly, from what I can find, he's only made one political donation, to Democrat Mihaela Elizabeth Plesa, TX House District 70.
"If you will not fight for right when you can easily win without blood shed; if you will not fight when your victory is sure and not too costly; you may come to the moment when you will have to fight with all the odds against you and only a precarious chance of survival. There may even be a worse case. You may have to fight when there is no hope of victory, because it is better to perish than to live as slaves." - Sir Winston Churchill