In the USA, that's the 3RD such major 'incident' involving mass killings by firearms this year.
In China, that was the only such 'incident' in two years; and it came nowhere close to having a number of casualties (as in, killed victims) in the dozens.
China has ~1,3 BILLION inhabitants; USA, ~315 millions.
The imbalance is obvious to anyone who cares to look.
There will always be depressed losers who blame society for their problems. No type or amount of mental health care services will change this.
Where guns are NOT easy to obtain/NOT owned by anyone and his idiot cousin, they can't get one (meticulous, long-term planning is definitely not their strength).
Using knives/other such weapons requires training (and, again, meticulous, sustained effort is not their strength). Also, knives/etc are far from being as deadly as firearms - as the comparison between the number of victims in SUA and China attests to.
What does this mean?
In countries where firearms are NOT easily obtainable, such 'incidents' (crazies killing tens of people) are rare.
In countries where firearms are easy to obtain and, consequently, ubiquitous (such as the USA), such 'incidents' are not rare at all - quite the opposite.