BOSTON (REUTERS) - Thousands of law enforcement agents from around the country plan to attend a memorial on Wednesday for a campus police officer who authorities say was slain by the accused Boston Marathon bombers, and Vice-President Joe Biden is slated to speak at the ceremony.
The service at the Massachusetts Institute of Technology honours 26-year-old Sean Collier, who was shot and killed by Tamerlan and Dzhokhar Tsarnaev on the MIT campus on Thursday night.
The two ethnic Chechen brothers planted and detonated two pressure-cooker bombs near the finish line of the Boston Marathon on April 15, killing three people and injuring 264, authorities say. Ten people lost limbs in the bombing.
Authorities released videos and photos of the suspects, still unidentified at the time, on Thursday. Hours later, officer Collier, who had worked at MIT since January 2012, was shot and killed.
MIT cancelled Wednesday's classes in his honour and said thousands of law enforcement agents were expected to attend the memorial from around the country.
Top US security authorities faced a grilling on Tuesday about the handling of the Boston bombing investigation by lawmakers seeking answers to why Tamerlan Tsarnaev, flagged as a possible Islamist radical, was not tracked more closely.
Tamerlan Tsarnaev, 26, was killed in a shootout with police on Friday and Dzhokhar Tsarnaev, 19, was captured later that day. He lies wounded in a Boston hospital charged with using weapons of mass destruction.
Investigators have focused on a trip to Dagestan last year by the older Tsarnaev and whether he became involved with or was influenced by Chechen separatists or Islamist extremists there.
Russian authorities flagged him as a possible Islamist extremist in 2011. The FBI interviewed him in Massachusetts but found no serious reason for alarm.
Senators said after Tuesday's briefing by FBI Deputy Director Sean Joyce and other officials that there may have been a breakdown in communication that kept authorities from tracking his apparent radicalisation.
Senator Saxby Chambliss of Georgia, the ranking Republican on the Senate intelligence committee, said the briefing raised questions about the flow of information among law enforcement and intelligence agencies.
"I think there has been some stonewalls, and some stovepipes reconstructed, that were probably unintentional, but we've got to review that issue again, and make sure there is the free flow of information," he said.
"I can't say the FBI dropped the ball. I don't see anybody yet that dropped the ball," Mr Chambliss said. "That may develop."
The wife of Tamerlan Tsarnaev is assisting authorities and in absolute shock that her husband and brother-in-law were accused of the deadly blasts, her lawyer said.
"She cries a lot," attorney Amato DeLuca said of Ms Katherine Russell, 24, an American-born convert to Islam who married Tsarnaev in June 2010. "She can't go anywhere. She can't work." The sisters of the bombing suspects said they too did not know what had happened to their brothers.
Ms Ailina Tsarnaev, who lives in West New York, New Jersey, and her sister Bella issued a statement through their attorneys expressing their sadness over "such a callous act."
"As a family we are absolutely devastated by the sense of loss and sorrow this has caused," they said. "We don't have any answers but we look forward to a thorough investigation and hope to learn more."
Dzhokhar Tsarnaev's condition improved to "fair" from"serious" on Tuesday as he recovered from gunshot wounds at Beth Israel Deaconess Medical Centre, where in an impromptu hearing on Monday, he was charged with two crimes that could result in the death penalty if he were convicted.
Recovering enough to communicate by nodding his head and writing, the younger Tsarnaev has told authorities he and his brother acted alone, learned to build the bombs on the Internet and were motivated by a desire to defend Islam because of "the US wars in Iraq and Afghanistan," NBC News reported.