The surviving suspect in the Boston Marathon bombings acknowledged to the FBI his role in the attacks but did so before he was advised of his constitutional rights to keep quiet and seek a lawyer, officials said Wednesday.

It is unclear whether those statements before the Miranda rights warning would be admissible in a criminal trial and, if not, whether prosecutors even need them to win a conviction. Officials said physical evidence, including a 9 mm handgun and pieces of a remote-control device commonly used in toys, was recovered from the scene.

The suspect, Dzhokhar Tsarnaev, 19, told authorities that his older brother, Tamerlan Tsarnaev, 26, only recently recruited him to be part of the attack, two U.S. officials said. The CIA, however, named Tamerlan to a terrorist database 18 months ago, officials said Wednesday, an acknowledgment that will undoubtedly prompt congressional inquiry about whether investigators took warnings from Russian intelligence officials seriously enough.

The U.S. officials who spoke to The Associated Press were close to the investigation but insisted on anonymity because they were not authorized to discuss the case with reporters.

Tamerlan, whom authorities have described as the driving force behind the plot, was killed in a shootout with police. Dzhokhar is recovering in a hospital from injuries sustained during a getaway attempt.

Authorities had previously said Dzhokhar exchanged gunfire with them for more than an hour Friday night before they captured him inside a boat covered by a tarp in a suburban Boston neighborhood backyard. But two U.S. officials said Wednesday that he was unarmed when captured, raising questions about the gunfire and how he was injured.

More than 4,000 mourners at the Massachusetts Institute of Technology paid tribute to a campus police officer who authorities say was gunned down by the bombing suspects.

Among the speakers in Cambridge, just outside Boston, was Vice President Joe Biden, who condemned the bombing suspects as “two twisted, perverted, cowardly, knockoff jihadis.”

Investigators have said the brothers appeared to have been radicalized through jihadist materials on the Internet and have found no evidence tying them to a terrorist group.

Dzhokhar told the FBI that they were angry about the U.S. wars in Afghanistan and Iraq and the killing of Muslims there, officials said.

How much of those conversations will end up in court is unclear. The FBI normally tells suspects they have the right to remain silent before questioning them so all their statements can be used against them.

Under pressure from Congress, however, the Department of Justice has said investigators may wait until they have gathered intelligence about other threats before reading those rights in terrorism cases. The American Civil Liberties Union has expressed concern about that.

Regardless, investigators have found pieces of remote-control equipment among the debris and were analyzing them, officials said. One official described the detonator as “close-controlled,” meaning it had to be triggered within several blocks of the bombs.

An FBI affidavit said one of the brothers told a carjacking victim during their getaway attempt, “Did you hear about the Boston explosion? I did that.”

Officials also 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, two U.S. officials said.

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.”

Dzhokhar’s public defender had no comment on the matter Wednesday. His father has called him a “true angel,” and an aunt has insisted he’s not guilty.

The suspects’ parents, Anzor Tsarnaev and Zubeidat Tsarnaeva, plan to fly to the U.S. from Russia on Thursday, the father was quoted as telling the Russian state news agency RIA Novosti. The family has said it wants to take Tamerlan’s body back to Russia.

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.

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.

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.”

(AP)