Searching for answers in Boston

Police captured the remaining Boston Marathon bombings suspect late Friday after a day-long manhunt, days of anxiety, a firefight with police and the killing of a police officer. The focus has now turned to finding motives for the violence.

"The families of those killed so senselessly deserve answers," said President Barack Obama on Friday in an address to the nation.

The arrest of Dzhokhar Tsarnaev sparked celebrations throughout Boston, bringing him and his brother’s week of terror to a close. Tsarnaev, 19, is in serious condition at Beth Israel Deaconess Medical Center, suffering from gunshot wounds. His older brother, Tamerlan, 26, was killed on Thursday in a firefight with police.

Waiving Miranda

US officials and a special interrogation team are gearing up to question Dzhokhar, who cannot yet be interrogated owing to his injuries. He is currently under armed guard in the hospital.

When they are able to do so, investigators plan to interrogate Tsarnaev without reading him the warning usually given to suspects before they are questioned. The Miranda rights warning is usually issued so that subsequent statements are admissible in court.

According to a Justice Department official, the government will instead invoke a public safety exception to the warning in order to question Dzhokhar extensively about other potential explosive devices or possible accomplices.

A week of anxiety

The ethnic Chechen brothers are believed to be responsible for the twin bombings that killed three people and injured more than 180 near the finish line of the Boston Marathon on Monday.

The capture came four days after the bombings and just a day after the FBI released images of two young men suspected of using pressure-cooker explosives at the marathon.

On Thursday, the brothers carjacked a man in a Mercedes Benz in Cambridge and later released him unharmed. Later, they allegedly shot a Massachusetts Institute of Technology (MIT) police officer. A hunt for the stolen Mercedes led authorities to Watertown, where the suspects exchanged gunfire with police.

In the shootout, a transit police officer was critically wounded, and Tamerlan sustained fatal injuries. Investigators said Dzhokhar ran over his wounded brother in a bid to escape. The hunt for the younger brother continued into Friday, when police issued a city-wide lockdown.

Public transport was suspended, air space was restricted and the nearby universities were closed as officers combed the neighborhoods. An hour after lifting the lockdown, admitting the search had been fruitless, police got a tip from a resident who found the bloodied suspect in a boat in his backyard. Police were called to the scene, and Dzhokhar was taken into custody after an exchange of gunfire.

Searching for a motive

The Tsarnaev brothers come from a small community of Chechens in Kyrgyzstan, a largely Muslim nation. The family moved in 2001 to Dagestan, a federal republic of Russia in the North Caucasus region, which is home to a violent Islamist insurgency. The suspects’ parents still live there.

Federal officials did not have the brothers under surveillance, but the FBI said on Friday that it had interviewed Tamerlan in 2011 at the request of a foreign government. The matter was dropped when the FBI "did not find any terrorism activity, domestic or foreign."

Both of the brothers' parents have denied their sons could be capable of such crimes.

The Kremlin on Saturday said both the US and Russian presidents had agreed to increase cooperation on counter-terrorism following the bombings.

Investigators hope to quickly determine the motives for the bombing and deem whether the suspects acted alone.

tm/slk (AP, AFP, Reuters)