Boston Marathon bomber Dzhokhar Tsarnaev broke his silence on the death and devastation he caused two years ago with words that were not a political tirade or a justification.

He apologized to his victims and their families at his formal sentencing Wednesday in federal court.

"I am sorry for the lives that I've taken, for the suffering that I've caused you, for the damage that I've done — irreparable damage," the 21-year-old former college student said, speaking haltingly in his Russian accent.

But some bombing survivors saw his apology as disingenuous and incomplete.

"After we heard it, we wished we hadn't," said Lynn Julian, who suffered a traumatic brain injury and a back injury, and now suffers from post-traumatic stress disorder.

"He threw in an apology to the survivors that seemed insincere," she said.

U.S. Attorney Carmen Ortiz said Tsarnaev's statement was more noteworthy for what he didn't say.

"He didn't renounced terrorism. He didn't renounce violent extremism," she said.

After Tsarnaev said his piece, U.S. District Judge George O'Toole Jr. quoted a line from Shakespeare. "The evil that men do lives after them. The good is often interred with their bones," he said.

"So it will be for Dzhokhar Tsarnaev," the judge said, telling Tsarnaev that no one will remember that his teachers were fond of him, that his friends found him fun to be with or that he showed compassion to disabled people.

"What will be remembered is that you murdered and maimed innocent people, and that you did it willfully and intentionally," O'Toole said.

Tsarnaev looked down and rubbed his hands together as the judge pronounced his fate: execution, the punishment decided by the jury last month for the 2013 attack that killed three people and wounded more than 260 others.

The apology came after Tsarnaev listened for about three hours as a procession of 24 victims and survivors lashed out at him for his "cowardly" and "disgusting" acts.

"He can't possibly have had a soul to do such a horrible thing," said Karen Rand McWatters, who lost a leg in the attack and whose best friend, 29-year-old Krystle Campbell, was killed.

Campbell's mother, Patricia Campbell, looked across the room at Tsarnaev, seated about 20 feet away, and spoke directly to him.

"What you did to my daughter is disgusting," she said. "I don't know what to say to you. I think the jury did the right thing."

Rebekah Gregory, a Texas woman who lost a leg in the bombing, defiantly told Tsarnaev she is not his victim.

"While your intention was to destroy America, what you have really accomplished is actually quite the opposite — you've unified us," she said, staring directly at Tsarnaev.

Bill Richard, whose 8-year-old son Martin was the youngest person killed in the bombing, noted that his family would have preferred that Tsarnaev receive a life sentence so that he could contemplate his crimes.

Richard said his family has chosen love, kindness and peace, adding: "That is what makes us different than him."

Tsarnaev assured the survivors he was paying attention to their words.

"All those who got up on that witness stand and that podium relayed to us, to me — I was listening — the suffering that was and the hardship that still is, with strength and with patience and with dignity," he said.

The judge was required under the federal death penalty law to impose the jury's death sentence for an attack prosecutors said was carried out by Tsarnaev and his older brother, Tamerlan, to retaliate for U.S. actions in Muslim countries. Tamerlan, 26, was killed during a getaway attempt days after the bombings.

Tsarnaev's apology was peppered with religious references and praise of Allah. He asked that Allah have mercy upon him and his dead brother.

Tsarnaev will almost certainly be sent to the death row unit at the federal penitentiary in Terre Haute, Indiana, where Oklahoma City bomber Timothy McVeigh was executed. It could take years or even decades for his appeals to work their way through the courts.