A random act of violence can happen anywhere. Objectively, SF is not a dangerous city when it comes to violent crimes. In 2000s, SF was indeed a violent city with triple digit murders.
And Europe has 10x the rate of Asian cities. What’s your point ? Every country has their own nuances and a city within a country is not devoid of context
If you read the article, you'll find that SF is a dangerous city in which someone was just senselessly murdered.