China is so big! All violent incidents are “isolated”
According to some, all these incident are “isolated” but they never want to face the problem.
There are tons of “spirited” teens or 精神小伙/精神小妹 who are jobless and have nothing better to do. They are in a situation that they are able to live due to the low food cost but are unable to do anything significant as every other activities are exorbitantly expensive.
Thus, they form gangs to have a sense of purpose and incident like this become a daily occurrence.