I refer to earlier postings.
Well, things are getting clearer.
In December, many Beijing expats turned on their cellphones to find grim rumors buzzing on social media platform WeChat – foreigners, it seemed, were the victims of a series of attacks. The details in the rumors varied – sometimes it was Sanlitun, other times Wudaokou. Were the perpetrators driving a BMW or a van? Were they armed with baseball bats or metal rods?
The gang alleged to have been targeting foreigners with baseball has been caught. Police are now appealing for witnesses, details:
http://beijingcream.com/2015/01/arrested-local-gang-alleged-to-have-targeted-foreigners-with-bats/
and also a wider overview:
http://www.theworldofchinese.com/2015/01/group-accused-of-attacking-foreigners-arrested/

In short:
A trio of Chinese men armed with baseball bats and metal pipes has been detained, following a violent assault on students at one of Beijing’s best-known universities. The case bears strong similarities to a series of racially tinged assaults alleged to have recently occurred in several foreign-centric districts, including Sanlitun, Houhai and Wudaokou, in which foreign witnesses reported being attacked without provocation by local men carrying weapons and traveling in a vehicle. The incidents were widely reported on WeChat and discussed on local forums, such as Reddit, where many expressed concern about possible hate crimes.