It's poor use of English. Clearly, what was meant was that an alleged massacre had occurred and that the BCC (after the event) had a reporter on the alleged scene of the alleged crime to report what they observed.
As minor a point as this may be, I think it's indicative of the BBC's sloppy reporting standards. I used to think that the BBC was the gold standard when it came to the objective reporting of the news. I have disabused myself of this notion in recent years due to the advent of multiple TV news channels. I find it absolutely fascinating to watch the likes of Al Jazeera, Russia Today, Sky News and the BBC all report on exactly the same event. The amount of bias shown by certain channels with regards to certain issues is enlightening to say the least.
All of the aforementioned news channels are highly biased (depending on the news story they are reporting) and the BBC is no different; in fact I would go so far as to say the the BBC is one of the most biased news outlets that I have access to.