A jury in Boston voted Friday to execute Boston Marathon bomber Dzhokhar Tsarnaev, refuting his lawyers’ argument that he was pulled into the plot by his radicalized Muslim older brother and overcoming Massachusetts’ popular opposition to the death penalty.

Tsarnaev said nothing when the verdict was announced at about 3:30 p.m ET. He sat in his chair and swallowed, and remained expressionless as U.S. District Judge George O'Toole thanked members of the jury, some of whom wept.

After he is formally sentenced by O'Toole this summer, Tsarnaev will likely end up at the U.S. Bureau of Prison’s death row in Terre Haute, Indiana, where he is expected to embark on an appeals process that could last years before he is finally killed by lethal injection. At 21, he will become the youngest person on federal death row.

But in the short term, the sentence closes a major chapter in Boston’s recovery from the April 15, 2013 bombing, in which twin blasts rocked the race’s crowded downtown finish line, killing three spectators, injuring more than 260 others, and inflicting a grievous psychological wound on one of America’s oldest cities. The explosions, on a local holiday marking the opening battles of the Revolutionary War, were the worst act of terror on American soil since 9/11.

Whether the verdict brings Boston any closer to healing is an open question.

The parents of 8-year-old Martin Richard, the youngest of those killed in the bombing, publicly advocated against the death penalty, saying last month that the potentially drawn out appeals process could “prolong reliving the most painful day of our lives.”

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Denise and Bill Richard watched the verdict in the courtroom, and showed no emotion after it was read.

Other victims, and victims’ relatives, however, said they favored Tsarnaev’s execution.

Karen Brassard, who was wounded by shrapnel in the bombing and attended the trial, said she felt the jury's decision allowed her "breathe again."

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"Once the verdict came in, it was like, okay, we can start from here and go forward and really feel like it's behind us," Brassard said.

Boston Mayor Martin Walsh said he hoped the verdict would provide "a small amount of closure to the survivors, families, and all impacted by the violent and tragic events surrounding the 2013 Boston Marathon. We will forever remember and honor those who lost their lives and were affected by those senseless acts of violence on our city."

U.S. Attorney Carmen Ortiz, whose office prosecuted Tsarnaev, said the trial sent a message that America gives a fair shot at justice for its worst criminals, terrorists included. "Today is not a day for celebration," she said. "It is not a day for political or moral debate. It is a day for reflection and healing."

The verdict was delivered by the same jury that on April 8 convicted Tsarnaev of all 30 criminal counts against him, covering the bombing and its violent aftermath, including the killing of an MIT police officer and a shootout with police in which Tsarnaev’s co-conspirator older brother was killed.

Of those counts, 17 carried the possibility of execution.

The jury got the case on Wednesday and deliberated for 15 hours before reaching its verdict. The courtroom fell silent as it was read.

The jury agreed on death for six of the death penalty counts, all of which focused on Tsarnaev's detonation of a pressure-cooker bomb that killed Martin Richard and Chinese graduate student Lingzi Lu. The third person who died at the race, Krystle Campbell, was killed by a similar bomb detonated by the older brother, Tamerlan Tsarnaev.

The verdict came despite a distaste for capital punishment in Boston and across Massachusetts. The death penalty was banned in the state 1984, and a convict has not been executed there since 1947.

A Boston Globe poll published last month showed that fewer than 20 percent of state residents favored death for Tsarnaev, down from 33 percent in September 2013.

But Tsarnaev was tried in the federal system, which allows the death penalty. Only one other federal jury in Massachusetts has voted for death in modern history, in the 2004 trial of murderer Gary Lee Sampson. That penalty was thrown out on a technicality, and a jury will reconsider his sentence later this year.

From the start of the trial, Tsarnaev’s lawyers spent the bulk of their energy on sparing him from execution, effectively admitting his guilt on the first day of arguments. They instead focused on painting a portrait of his childhood in hopes that it would humanize him in the eyes of the jury and make less likely for the 12 members to condemn him to death. The lawyers elicited testimony from friends, classmates and relatives in an attempt to portray him as a young, impressionable man in the thrall of his brother, who lived with him after their parents moved back to their native Russia.

The defense’s case culminated with testimony from Sister Helen Prejean, an influential opponent of capital punishment who recalled meeting Tsarnaev in jail and concluding that he was “genuinely sorry.”

The defense sent the jury into deliberations with a list of “mitigating factors” that included his lack of prior history of violence, his susceptibility to his brother's behavior, his brother’s planning of the attack and their father’s mental illness, which the lawyers said led the brother to becoming the family’s dominant male.

That strategy, led by renowned defense attorney Judy Clarke, failed.

Instead, the jury seemed to back prosecutors who argued that Tsarnaev was a willing and equal partner with his brother, who was killed in the showdown with police.

Prosecutors argued that Dzhokhar Tsarnaev's crimes met several legal thresholds to warrant execution — including that multiple people were killed or injured, including an 8-year-old boy; that "substantial planning and premeditation" went into the crimes; and the "heinous, cruel and depraved manner" in which they were committed.

The government raised additional "aggravating factors," including the "betrayal of the United States," the selection of an "iconic event" as a target, the death of a police officer, statements in which Tsarnaev encouraged "others to commit acts of violence and terrorism," the trauma unleashed on victims' families, and Tsarnaev's apparent lack of remorse.

In his closing remarks, Assistant U.S. Attorney Steven Mellin called Tsarnaev a coldhearted terrorist.

"The defense will ask you to value the defendant's life, but he did not value the lives of his victims, not even the lives of children,” Mellin said. “He killed indiscriminately to make a political statement, and he placed no value on the lives and didn't care for a second what impact his actions and his killings would have on so many other innocent family members and friends. His actions have earned him a sentence of death.”

The jury agreed.