It's interesting that some people keep the need to point out that Sikhs are not Muslim. Yes, they are not Muslim, they're not Hindu as well, however jumping to clarify difference leaves the (albeit perhaps "unintentional") perception that there is something decidedly wrong with those "others". #RIP #Condolences
The hidden notion in many comments about this is that, had they been Muslims, this would somehow be "deserved". The fact is that no one, Muslim, Sikh, Jew, Christian deserve this. Now a mosque has been burned in Joplin and the main theme here is the inability to tolerate differences.