As The Onion says.

"No way to prevent this", says only nation where this always happens.

So you want to use the gang-ridden state of third world countries as the bar for acceptability for the United States?

When was the last time someone managed to stab 13 people in London? 

Are you suggesting that unless we can stop all forms of violence, that gun control shouldn't happen?

If anything, that means Gun control has worked as someone was stabbed and not shot?

Apparently, the person who committed the mass shooting doesn't have a criminal record outside of speeding tickets. If this is true, I don't know how we could've restricted his gun rights. We could say anyone who had ptsd can't have a gun, but that will result in people not getting any help and probably cause more mass shootings.

Your slippery slope fallacy doesn't happen here though?

the OP links to a cnn page, where theres articles related to this situation.

articles like :

Neighbor said shooter's mother "lived in fear"  (police had been called to home a few times)
Hes even had mental health specialists with them out to the house to talk to him before.
They cleared him (he wasnt crazy enough for them to do anything about it, I guess).

I think there was something about domestic violence too...  cant find atm.
So its not true he just had speeding tickets.
His family + police knew he wasnt "quite" right in the head, yet he still got to keep his gun.

"We could say anyone who had ptsd can't have a gun, but that will result in people not getting any help and probably cause more mass shootings."

That makes alot of sense actually imo.
People who have had mental break downs before, probably shouldnt own a gun.
Even if its been years without them haveing another break down.

Because a lot of military members along with Americans, in general, WANT to keep their guns and will be afraid to get help (admit they have ptsd or any mental issues) if it stops them from having guns. They will stay silent until one day they explode and people get hurt.

Edit: Answered my question in a prior post.

No, not at all. Please don't put words in mouth.

The hyperbole from people who don't live in the US is tiring. There's never any genuine conversation.