When two bombs exploded near the finish line of the Boston Marathon on Monday, many photojournalists were already at the scene, watching as one of the world's best-known running competitions turned to confusion and terror.
"The Marathon finish line scene is usually one of celebration," photographer Ken McGagh told the MetroWest Daily News. "People were initially eerily quiet" after the blasts.
Here, police officers draw their guns as 78-year-old marathon runner Bill Iffrig is knocked to the ground from the force of the first explosion, yards from the finish line on Boylston Street.
Smoke in the Streets
Rescuers tend to the injured after the Monday explosions, as a cloud of smoke hovers over the sidewalk; over 100 people were hospitalized with injuries from the two blasts.
An injured man lies outside the Marathon Sports storefront. The windows of several buildings on Boylston Street were blown out by the explosions.
Helping the Wounded
Boston Marathon participant Robert Wheeler, 23, of Ashland, Massachusetts, kneels to help an injured man. In an address on April Tuesay, President Barack Obama spoke of the "exhausted runners who kept running to the nearest hospital to give blood, and those who stayed to tend to the wounded."
Carlos Arredondo leaves the scene of the bombs on Monday. According to the New York Times, Arredondo has been handing out flags to Boston Marathon runner since his son, a Marine, was killed in Iraq in 2004.
This photo, produced by the Joint Terrorism Task Force of Boston, shows what was left of one of the devices after it exploded.
Searching for Answers
Investigators hunt for evidence at the site of one of the blasts. Gunpowder and shrapnel housed in a pressure cooker caused at least one of the explosions.
Patroling the Area
U.S. Army soldiers walk toward the bomb sites on the day after the explosions.
Boston Marathon runners (left to right) Lisa Kresky-Griffin, Diane Deigmann and Tammy Snyder stand with their arms around each other at the entrance to Boylston Street, blocked off a day after the two bombs exploded.
Well-wishers gather with candles on Tuesday to memorialize Martin Richard, an 8-year-old boy from Dorchester, Massachusetts, who was killed in one of the explosions at the Boston Marathon.
Paying Respects to the Victims
A vigil is held on Boston Common on Tuesday to commemorate the bombing victims.
A Child, Taken Away
Martin Richard, 8, was waiting at the finish line to hug his father, a runner in the Boston Marathon, when the blasts went off. Richard was named as one of the three victims.
Authorities say that the bombing suspects shot and killed a campus police officer at the Massachusetts Institute of Technology on Thursday night, spurring police to issue a "shelter in place" warning for much of the Boston area.
Hunt for Suspects
On Friday, SWAT teams were deployed across Watertown, Massachusetts, in search of the remaining suspect, Dzhokar Tsarnaev. The other suspect, Dzhokar's older brother, Tamerlan, was reportedly killed by police early Friday.
A resident looks on as police search an apartment complex for the second suspect in Watertown, Massachusetts on Friday.