THIS chilling image shows a mystery figure lurking on a rooftop – as a bomb blast rips through the Boston Marathon finishing line below.
The person does not seem to react as the ground-floor of the building erupts into flames following the second explosion.
The image was posted on Twitter shortly after the devastating attack – which killed at least three and injured over 140 innocent bystanders.
It was not immediately clear whether the figure on the roof had anything to do with the terror attack.
But some claim it raises the unnerving possibility that a perpetrator watched on as the street-level carnage was unleashed.