Photos: Boston Marathon explosions

In this image from video provided by WBZ TV, spectators and runners run from what was described as twin explosions that shook the finish line of the Boston Marathon. Two explosions shattered the euphoria of the Boston Marathon finish line on Monday, sending authorities out on the course to carry off the injured while the stragglers were rerouted away from the smoking site of the blasts. (WBZ-TV/AP)
People react as an explosion goes off near the finish line of the 2013 Boston Marathon in Boston, Monday, April 15, 2013. Two explosions went off at the Boston Marathon finish line on Monday, sending authorities out on the course to carry off the injured while the stragglers were rerouted away from the smoking site of the blasts. (AP Photo/The Boston Globe, David L Ryan)
Rescue personnel aid injured people near the finish line of the 2013 Boston Marathon following explosions in Boston, Monday, April 15, 2013. Two explosions shattered the euphoria of the Boston Marathon finish line on Monday, sending authorities out on the course to carry off the injured while the stragglers were rerouted away from the smoking site of the blasts. (AP Photo/The Boston Herald, Stuart Cahill)
Medical workers aid an injured man at the 2013 Boston Marathon following an explosion in Boston, Monday, April 15, 2013. Two bombs exploded near the finish of the Boston Marathon on Monday, killing at three people, injuring over 140 others and sending authorities rushing to aid wounded spectators.(AP Photo/The Boston Globe, David L. Ryan)
A Boston Marathon competitor and Boston police run from the area of an explosion near the finish line in Boston, Monday, April 15, 2013. (AP Photo/MetroWest Daily News, Ken McGagh)
One of the blast sites on Boylston Street near the finish line of the 2013 Boston Marathon is investigated by two people in protective suits in the wake of two blasts in Boston Monday, April 15, 2013. (AP Photo/Elise Amendola)
Amtrak Explosive Detection K-9 officer Kenneth Wolf and his dog Teddy patrol the station tunnels at Union Station in Los Angeles, Monday, April 15, 2013. The city increased security following bomb explosions in Boston that killed two people and injured more than 80 near the crowded finish line of the Boston Marathon.(AP Photo/Damian Dovarganes)
A Phoenix Coyotes fan holds up a sign as a tribute to the victims of the bombing at the Boston Marathon in the second period during an NHL hockey game, on Monday, April 15, 2013 in Glendale, Ariz
Shane Magness, a student at Oklahoma Christian University, bows his head in prayer for the victims of the Boston Marathon bombing, at the Oklahoma City National Memorial in Oklahoma City, Monday, April 15, 2013. On Friday, Oklahoma City will observe the 18th anniversary of the April 19, 1995, bombing of the Alfred P. Murrah Federal building that killed 168 people and injured hundreds more. (AP Photo/Sue Ogrocki)
Former Los Angeles Lakers center Kareem Abdul-Jabbar, left, and actor Harrison Ford observe a moment of silence for the victims of the bombing in Boston prior to the Los Angeles Dodgers' baseball game against the San Diego Padres, Monday, April 15, 2013, in Los Angeles. (AP Photo/Mark J. Terrill)