A lot of people are thinking that.
I suspect it to be true, and my brother called me with the exact same suspicion. I don't know why, because so far absolutely no information has been made public about the motivations or ideologies of the perpetrators. The authorities may not even know themselves, or if they know, they may choose not to publicize it for reasons of their own.
Its still a little early to tell anything. Speculations have a way of becoming accepted as fact, it pays to be cautious at this point.