Timeline of the Boston bombings investigation - in pictures

Runners continue towards the finish line of the Boston Marathon as an explosion erupts near the finish line of the race in this photo licensed to Reuters by photographer Dan Lampariello in Boston, Massachusetts, on Monday, April 15. Two explosions seconds apart ripped through the crowd Photograph: Reuters

A second explosion goes off roughly 12 seconds after the first near the finish line Photograph: Boston Globe via Getty Images

Police officers with their guns drawn hear the second explosion down the street. The first explosion knocked down 78-year-old Bill Iffrig near the finish line. He got up and finished the race Photograph: Boston Globe via Getty Images

From left, Martin Richard, 8, Krystle Campbell, 29, and Lingzi Lu, are the three people killed in the explosions. More than 170 others were wounded, many with injuries that led to amputations Photograph: AP

A man in a bomb-disposal suit investigates the site of the explosion. Boylston Street was closed off for the rest of the week as investigators collected evidence of the bombs, including the lid to a pressure cooker on the roof on a nearby building Photograph: Jessica Rinaldi/Reuters

People gather with candles during a vigil at Garvey Park in Boston for eight-year-old Martin Richard on Tuesday night. Richard was the first victim to be publicly identified Photograph: Jared Wickerham/Getty Images

A mourner reacts during a candlelight vigil at City Hall in Cambridge on Wednesday night. Vigils were held in public squares, parks and churches throughout the Boston area Photograph: Matt Rourke/AP

On Thursday morning, President Barack Obama attended an interfaith prayer service at the Cathedral of the Holy Cross in Boston, decrying the bombers as "small, stunted individuals who would destroy rather than build, and think that somehow that makes them important" Photograph: Spencer Platt/Getty Images

At the service, Boston mayor Thomas Menino rose out of a wheel chair and stood in front of a packed church of 1,700 Bostonians to say: “We will not be brought down. This is Boston, a city of courage, compassion and strength that knows no bounds" Photograph: Spencer Platt/EPA

Late Thursday afternoon – as internet sleuths were circulating photos of possible suspects – the FBI held a press conference to release images of the two men they wanted to question Photograph: Reuters

On Thursday, hours after the FBI publicised surveillance footage showing two men wanted for questioning, Tamerlan Tsarnaev and Dzhokhar Tsarnaev allegedly killed an MIT police officer, critically injured a transit officer in a firefight and threw explosive devices at police during a getaway attempt in a long night of violence that left Tamerlan dead and Dzhokhar on the run Photograph: Mario Tama/Getty Images

Police officers (not pictured) keep a man on the ground in Watertown following the shooting of the MIT police officer. As police pieced together the fast-moving events, anyone on the nearby streets was at first considered a suspect Photograph: Brian Snyder/Reuters

Many woke up on the east coast on Friday morning to the news that Tamerlan Tsarnaev, 26, left, and Dzhokhar Tsarnaev, 19, had been identified as suspects Photograph: AP

When Dzhokhar Tsarnaev fled the shootout that left his brother dead, authorities shut down Watertown, Massachusetts, to search for him. The manhunt kept residents in their homes through most of Friday as agents searched house-by-house Photograph: Darren McCollester/Getty Images

Watertown residents were told to stay inside all day Friday as police in tactical gear conducted the search Photograph: Matt Rourke/AP

The shelter-in-place order was soon expanded to the entire Boston area, and public transit was shut down. The streets and sidewalks around the Rose Kennedy Greenway in Boston were almost deserted at dinnertime Friday Photograph: Elise Amendola/AP

Ruslan Tsarni, uncle of the Tsarnaev brothers, addressed the media from his Montgomery Village, Maryland, home and urged Dzhokhar to turn himself in Photograph: Allison Shelley/Getty Images

A look through the sealed-up door to an apartment used by the Tsarnaev brothers in Cambridge Photograph: Dominick Reuter/EPA

With the manhunt under way in Boston, Obama meets with members of his national security team to discuss the investigation. Seated with the president are FBI director Robert Mueller; Lisa Monaco, assistant to the president for homeland security and counterterrorism; attorney general Eric Holder; deputy national security advisor Tony Blinken; and vice-president Joe Biden. Photograph: The White House/Getty Images

Shortly after police lifted the order requiring residents to stay indoors, a Watertown resident found the suspect in the stern of his boat, bleeding and in a serious medical condition, drawing hundreds of police officers in response Photograph: Jared Wickerham/Getty Images

Police wait at the end of Franklin Street and a police helicopter searchlight beams down as Swat crews prepare to apprehend Boston Marathon bombing suspect Dzhokhar Tsarnaev Photograph: Dominic Chavez/EPA

Dzhokhar Tsarnaev's body gives off a heat signature in an infrared image taken by Massachusetts State Police from a helicopter above Photograph: Handout/Getty Images

After a tense standoff in the boat, Dzhokhar Tsarnaev is apprehended by police. ATF and FBI agents check Tsarnaev for explosives and also give him medical attention after he was apprehended in Watertown Photograph: AP

News of Tsarnaev's arrest was greeted with celebrations on Franklin Street Photograph: Julio Cortez/AP

Neighbors use cameras to record images of the boat on Franklin Street where Dzhokhar Tsarnaev was hiding late Friday night Photograph: Lucas Jackson/Reuters

Connor Walsh of Boston University holds American flag while celebrating in the Boston Common after Tsarnaev was taken into custody Photograph: Boston Globe via Getty Images

By Sunday, as investigators built their criminal case against Tsarnaev, attention on Boylston Street turned to memorialising Sean Collier, the MIT police officer who was shot dead, and MBTA officer Richard Donahue Jr, who was shot and injured Photograph: Jim Bourg/Reuters

On Sunday, people wait on line to attend a wake in Medford, Massachusetts, for 29-year-old Krystle Campbell, one of three people killed in bombings. A private funeral was held Monday for the 29-year-old restaurant manager who was raised in Medford Photograph: Mario Tama/Getty Images