Update - Sunday Aug. 10, 8 pm: Chinese police reached the preliminary conclusion that Tang Yongming lost his will to live due to personal adversity, and took his anger out on society, which produced his extreme action.
Saturday morning: I was going to write about the Olympics opening ceremony, which evoked all kinds of reactions from American and Chinese alike, but the news this morning about the stabbing death of an American tourist shocked and deeply saddened me. The killer's motivation is a mystery as attacks on foreigners in Beijing are extremely rare. The attacker's name is 唐永明 (Tang Yongming), and there is speculation by Chinese netizens – someone on Sohu.com has found an internet profile of a man whose name, age and hometown match the attacker's. The profile shows the man as a stock market regular. If this proves to be the same man, then his action might have something to do with the falling stock market in China.
Added at 10 am: now all Chinese posts I saw earlier about this incident have been removed.