Dzhokhar Tsarnaev, the 21-year-old man convicted of carrying out a deadly terrorist attack at the Boston Marathon in April 2013, has been sentenced to death.

After a near-15 hour deliberation on whether Tsarnaev should be put to death or spend life in prison for his crime, the jury of seven women and five men in the high profile and protracted case returned to the court Friday afternoon to announce their decision.

The jury found Tsarnaev guilty last month of all 30 charges leveled against him — 17 of which could have sent him to the execution chamber.

Tsarnaev's face is well known across the country, perhaps more so than his brother and co-conspirator Tamerlan, who died in a shootout with police in Boston four days after the attack. The two bombs planted by the brothers killed three people, including an 8-year-old boy, and injured as many as 260 others. Witnesses described the scene as chaotic, with people, blood, and debris flying in every direction.

The aftermath of the Boston bombing in April 15, 2013.

On Friday, Tsarnaev sat in silence in the court as the verdict was announced around 3:30 PM. It was delivered despite a moratorium on death penalty sentences in Massachusetts that has been in place since 1984. Tsarnaev, who was tried federally, is now the youngest person on federal death row. He is likely to appeal the sentencing, which could initiate a process that will take years to complete.

The jury's decision brings some closure to Boston after a long period of grieving for those who lost their lives, limbs, and loved ones in the bombing that has been branded the worst terror attack on American soil since 9/11.

Some of the victims and families had come out against giving Tsarnaev the death penalty, but others have supported his execution.

Boston Mayor Martin J. Walsh thanked the jurors and judge for their roles in the trial in a statement on Friday.

" I hope this verdict provides a small amount of closure to the survivors, families, and all impacted by the violent and tragic events surrounding the 2013 Boston Marathon," he said. "We will forever remember and honor those who lost their lives and were affected by those senseless acts of violence on our City. Today, more than ever, we know that Boston is a City of hope, strength and resilience, that can overcome any challenge."

Throughout the trial, Tsarnaev's lawyers attempted to secure a sentence of life in prison. The attorneys did not argue their client's innocence, attempting instead to humanize him by detailing his childhood and upbringing and paint him as a impressionable young man who was misled by the religious fanaticism of his elder brother.

Tsarnaev immigrated from Russia's Caucasus region with his family to Cambridge, Massachusetts, in 2002. His lawyers presented "mitigating factors" in the case to the jury before deliberations, including arguments that his brother masterminded the attack and that his father's mental illness had elevated Tamerlan's role as head of the family in his brother's eyes. But the jury was not swayed.

Instead they agreed with prosecutor Steven Mellin, who said in his closing arguments that "the only sentence that will do justice in this case is a sentence of death."

"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."

Criminal law professor Charles P. Ewing, who directs the Advocacy Institute at the State University of New York at Buffalo, told VICE News he is not surprised about the outcome of today's sentencing, given that all of the jurors in the case were required to be "death qualifying" — meaning they were only allowed to serve if they were willing to impose the death penalty.

"I think the defense did a good job in presenting what mitigation there was for the defendant, but the prosecution did an equally good job in painting the horrific nature of the crime," Ewing said. "They basically put the victims of the crime in the jury's face."

Ewing added that he anticipates a lengthy appeals process, saying it is likely that, "When all is said and done the death penalty will be upheld, but it will take many years."