This is the kind of story that folks who are familiar with American gun culture hear all the time, but folks who aren’t close to the culture seem to never hear about.
The two key things to point out are that first: yes, an armed citizen can stop an in-progress attack. No one was killed in this incident, but the two stabbing victims were injured “critically”, so this was a life-threatening incident. Secondly: concealed-carry holders (I’m assuming he had a permit) are not prone to just opening fire at the smallest provocation, putting innocent lives at risk.
I’m also curious about why the attacker shouted “You killed my people!” as he began stabbing, but rather than speculate I’ll just wait for more information on that. (Article here.)