Boston Marathon bombs
On April 15, 2013, two bomb blasts rocked the annual Boston Marathon, injuring more than 170 people and killing three others: Martin Richard, 8; Krystle Campbell, 29; and Lu Lingzu, 23, a Chinese student at Boston University. The suspects later forced a standoff with authorities. They were identified as two ethnic Chechen brothers from southern Russia who had been in the US for about a decade, 19-year-old Dzhokhar Tsarnaev and his 26-year-old brother, Tamerlan, who died in the gun battle. Dzhokhar was arrested on April 19, 2013.
US stages massive manhunt for Boston bomber
United States investigators yesterday stepped up their search for the attacker or attackers who devastated the Boston Marathon with two bombs that killed three people and hurt more than 170, many of whom suffered horrific injuries.
Boston's Boylston Street, scene of the finishing-line carnage, remained sealed off as investigators sought leads in the worst bombing in the US since the September 11 attacks.
President Barack Obama call the bombing an act of terrorism. "This was a heinous and cowardly act," Obama said. "Any time bombs are used to target innocent civilians, it is an act of terror."
Richard DesLauriers, the FBI's chief agent in Boston, vowed to go to "the ends of the earth" to find those responsible.
While police searched the flat of a "person of interest", and a Saudi man remained under guard in hospital, there were no convincing answers for a city in mourning.
The two bombs went off 13 seconds and about 100 metres apart.
The dead and injured were aged between two and 71. Among those killed was eight-year-old local boy Martin Richard. His mother and sister, who lost a leg, were among 17 people critically injured. Nine children were among those hurt.
Most of the 23,000 runners in the race had finished when the first bomb exploded behind a row of national flags, four hours and nine minutes after the race began. It is believed the blasts were timed for maximum carnage. Several of the wounded lost limbs in the blasts.
The explosives were made of six-litre pressure cookers packed with metal and ball bearings and placed in duffel bags, a person briefed on the investigation said.
"We saw people with their legs blown off," witness Mark Hagopian said. "A person next to me had his legs blown off at the knee - he was still alive."
Despite earlier fears, Massachusetts Governor Deval Patrick said no additional explosive devices were found.
In the wake of the attack, armed National Guard troops and police patrolled Boston commuter trains and buses. Tight security is likely for several days. New York, Los Angeles, San Francisco and several other major US cities also put extra police on the streets.
No group had come forward to claim responsibility for the attack, and officials said there had been no intelligence warnings. The Pakistani Taliban, which has threatened attacks in the US because of its support for the Pakistani government, yesterday denied any role in the bombings.
As the search for the bomber or bombers was stepped up, investigators searched a flat in the Boston suburb of Revere and took away bags after a man described as "a person of interest" was stopped.
DesLauriers said investigators had received "voluminous tips".
"We will go to the ends of the earth to identify the subject or subjects who are responsible for this despicable crime, and we will do everything we can to bring them to justice," he said.
Additional reporting by Reuters, Associated Press