Here is video footage of the moment two explosions hit the Boston Marathon - leaving three dead and more than 100 injured.<br /><br />The focus in Boston right now is finding out who is responsible for the blasts.<br /><br />Former CIA agent Robert Grenier says the significance of when the attack happened could be a clue.<br /><br />"One wonders if perhaps there might not be a domestic right-wing terrorist component to this," he told Al Jazeera.<br /><br />Watch a highlight of the interview and amateur footage of the second explosion here.
