This could be so many things. The possibilities are as vast as the universe itself. Even if we presume it pertains to intelligent life-forms and not to some natural phenomena (that we may not even know of!), it could very well be something that is not directed at someone in particular (not actual communication but a result/consequence of something else) or that it may be an occurrence that is beyond our scope of (current) understanding. I am not saying that "if we'd be there/closer, we'd understand", I'm saying we could very well be unable to understand due to our current genetic limitations. Anyways, pretty interesting stuff.