An Iraqi woman grieves at the scene of a bomb attack in Jameela market in the Iraqi capital's crowded Sadr City neighborhood Baghdad, Iraq, Thursday, August 13, 2015. A massive truck bomb ripped through a popular Baghdad food market in a predominantly Shiite neighborhood in the early morning hours on Thursday, killing dozens of people, police officials said. (Photo by Karim Kadim/AP Photo)
This combination of April 15, 2013 and April 2, 2014 photos show a police officer clearing Boylston Street following a bomb blast near the finish line of the 2013 Boston Marathon, and pedestrians crossing at the same corner nearly a year later in Boston. (Photo by Charles Krupa/AP Photo)
Women comfort each other as they mourn over the death of a family member who was killed in a bomb blast, at a local hospital in Lahore, Pakistan, Sunday, March, 27, 2016. A bomb blast in a park in the eastern Pakistani city of Lahore has killed tens of people and wounded scores, a health official said. (Photo by K.M. Chuadary/AP Photo)
A man smiles as he carries firewood he bought on a street amid ongoing fuel and cooking gas shortages in Yemen's capital Sanaa December 2, 2015. (Photo by Khaled Abdullah/Reuters)
A Felix Airways plane is seen after it was destroyed by an airstrike at the international airport of Yemen's capital Sanaa, April 29, 2015. Jets from a Saudi-led alliance destroyed the runway of Yemen's Sanaa airport on Tuesday to prevent an Iranian plane from landing there, Saudi Arabia said, as fighting across the country killed at least 30 people. Airport officials said the strikes set a civilian aircraft operated by Yemeni Felix Airways ablaze. (Photo by Khaled Abdullah/Reuters)