Is Boston bombing domestic or international terrorism?

Is Boston bombing domestic or international terrorism?
ADDS IDENTIFICATION OF RUNNER- BILL IFFRIG- Bill Iffrig, 78, lies on the ground as police officers react to a second explosion at the finish line of the Boston Marathon in Boston, Monday, April 15, 2013. Iffrig, of Lake Stevens, Wash., was running his third Boston Marathon and near the finish line when he was knocked down by one of two bomb blasts. (AP Photo/The Boston Globe, John Tlumacki)

9/11 Commission member and former Washington US Senator, Slade Gorton, examines the investigation into the Boston bombing and what questions authorities need to focus on to find answers about this terrorist attack.