Three of six customers stabbed are in critical condition.
The stabber was shot and killed within a minute of the attack.
How many of the 6 would have died if someone armed with firearms had not stopped him? At least 3 may still die, or suffer lifelong disabilities from the injuries.
Arguing that knives are a less lethal option than firearms ignores the obvious advantages knives offer. No background checks, no waiting periods, no limits on the types of knives you can own with few exceptions based on locale, no ammunition cost, no magazine capacity limits, no noise to alert others of the attack, etc. etc.
You might be able to hit someone from a greater distance with a firearm, but a nice bow or crossbow can do that, too.
The authorities knew this person was dangerous, but they did nothing more than follow him. Apparently, police there have no duty to protect individuals from violent people, just like the US.