Among the speakers at the memorial service in Cambridge, just outside Boston, was Vice President Joe Biden, who condemned the bombing suspects as "two twisted, perverted, cowardly, knockoff jihadis."
In a striking new development, U.S. officials said the name of the dead suspect, Tamerlan Tsarnaev, was added by the CIA to a terrorist database 18 months ago. The officials spoke to The Associated press on the condition of anonymity because they were not authorized to speak publicly about the ongoing case.
The disclosure was significant because officials have been saying the U.S. intelligence community had no relevant information leading up to the April 15 bombings, which killed three people and injured more than 260 others. Inclusion of one of the bomb suspects' name in a database for 18 months before the attack could prompt congressional inquiries about whether the U.S. government adequately investigated tips from Russia that Tsarnaev posed a security threat.
Tsarnaev's younger brother, surviving suspect Dzhokhar Tsarnaev, 19, was listed in fair condition as he recovered from wounds suffered during a getaway attempt. He could get the death penalty if convicted of plotting with his older brother to set off the pressure-cooker bombs near the marathon's finish line. Tamerlan Tsarnaev, 26, died in a shootout with police.
Dzhokhar Tsarnaev's father has called him a "true angel," and an aunt has insisted he's not guilty. His public defender didn't immediately return a call seeking comment Wednesday.
The bombs were triggered by a remote detonator of the kind used in remote-control toys, U.S. officials said Wednesday. They said investigators found pieces of the remote-control equipment among the debris and were analyzing them.
Both U.S. officials are close to the ongoing investigation but spoke on condition of anonymity because they were not authorized to discuss it publicly. One official described the detonator as "close-controlled," meaning it had to be triggered within several blocks of the bombs.
The criminal complaint filed against Dzhokhar Tsarnaev said he was using a cellphone moments before the blasts.
U.S. officials also said he has told interrogators he and his brother were angry about the U.S. wars in Muslim Afghanistan and Iraq.
After closed-door briefings on Capitol Hill with the FBI and other law enforcement officials, lawmakers said earlier this week that it appeared so far that the brothers were radicalized via the Internet instead of by direct contact with any terrorist groups and that the older brother was the driving force in the bomb plot.
In Russia, U.S. investigators traveled to the predominantly Muslim province of Dagestan and were in contact with the brothers' parents, hoping to gain more information.
The parents, Anzor Tsarnaev and Zubeidat Tsarnaeva, plan to fly to the U.S. on Thursday, the father was quoted as telling the Russian state news agency RIA Novosti. The family has said it wants to bring Tamerlan Tsarnaev's body back to Russia.
Investigators are looking into whether Tamerlan, who spent six months in Russia's turbulent Caucasus region in 2012, was influenced by the religious extremists who have waged an insurgency against Russian forces in the area for years. The brothers have roots in Dagestan and neighboring Chechnya but had lived in the U.S. for about a decade.
There was a new twist in the accounts of how Dzhokhar Tsarnaev was captured last week.
Two U.S. officials say he was unarmed when police captured him hiding inside a boat covered by a tarp in a neighborhood backyard. Authorities originally said they had exchanged gunfire with him for more than one hour Friday evening before they were able to subdue him.
The U.S. officials, speaking on condition of anonymity because they were not authorized to discuss the ongoing investigation, said investigators recovered a 9 mm handgun believed to have been used by Tamerlan from the site of a Thursday night gunbattle that injured a Massachusetts Bay Transportation Authority officer. Dzhokhar was believed to have been shot before he escaped.
The officials told the AP that no gun was found in the boat. Boston police Commissioner Ed Davis said earlier that shots were fired from inside the boat.
Asked whether the suspect had a gun in the boat, Davis said, "I'm not going to talk about that."
Kurt Schwartz, director of the Massachusetts Emergency Management Agency, did respond to the report.
"Within half a mile of where this person was captured, a police officer was shot. And I know who shot him." Schwartz said. "And there were three bombs that went off, and I know where those bombs came from. ... To me, it does not change anything. This guy was captured alive and will survive. True or not true, it doesn't change anything for me."
At MIT, bagpipes wailed as students, faculty and staff members and throngs of law enforcement officials paid their respects to MIT police Officer Sean Collier, who was ambushed in his cruiser three days after the bombing.
The line of mourners stretched for a half-mile. They had to make their way through tight security, including metal detectors and bomb-sniffing dogs.
Boston native James Taylor sang "The Water is Wide" and led a sing-along of "Shower the People."
Biden told the Collier family that no child should die before his or her parents, but that, in time, the grief will lose some of its sting.
"The moment will come when the memory of Sean is triggered and you know it's going to be OK," Biden said. "When the first instinct is to get a smile on your lips before a tear to your eye."
The vice president also sounded a defiant note.
"The purpose of terror is to instill fear," he said. "You saw none of it here in Boston. Boston, you sent a powerful message to the world."
In another milestone in Boston's recovery, the area around the marathon finish line was reopened to the public, with fresh cement still drying on the repaired sidewalk. Delivery trucks made their way down Boylston Street under a heavy police presence, though some damaged stores were still closed.
"I don't think there's going to be a sense of normalcy for a while," Tom Champoux, who works nearby, said as he pointed to the boarded-up windows. "There are scars here that will be with us for a long time."
Associated Press writers Bridget Murphy and Bob Salsberg in Boston, Lynn Berry in Moscow, and Kimberly Dozier, Adam Goldman, Eric Tucker, Matt Apuzzo, and Eileen Sullivan in Washington contributed to this report.