Boston (CNN) A federal jury Friday sentenced Boston Marathon bomber Dzhokhar Tsarnaev to death, the final chapter to a brutal, emotionally exhausting trial that brought forth indelible images of an unspeakable crime .

There was no visible reaction from Tsarnaev, 21. Several survivors and relatives of victims dabbed tears in the quiet courtroom.

Bill and Denise Richard, parents of the bombing's littlest victim, 8-year-old Martin, looked on stoically from the second row. They were against the death penalty.

The verdict marked the first time in the post-9/11 era that federal prosecutors have won the death penalty in a terrorism case.

Tsarnaev could be sent to death row in Terre Haute, Indiana, but his final destination will not be known until after the judge formally sentences him in court. No sentencing date has been set.

The six counts that brought Tsarnaev a death sentence all relate to the second of two pressure-cooker bombs, which caused the explosion on Boylston Street in front of the Forum restaurant on April 15, 2013. He was not sentenced to death for the first bomb, which was planted by his brother, Tamerlan, nor for the shooting death of MIT officer Sean Collier

As the lengthy verdict was read, Tsarnaev stood with his head bowed, hands clasped in front of him.

U.S. District Court Judge George O'Toole thanked the defendant's lawyers and added, "Mr. Tsarnaev has comported himself with propriety."

When the jury left the courtroom one last time, O'Toole said, "And so, jurors, this is it." As U.S. marshals stepped forward to take Tsarnaev away, he gave a wry smile.

My mother and I think that NOW he will go away and we will be able to move on. Justice. In his own words, "an eye for an eye". — Sydney Corcoran (@Sydney23Lynne) May 15, 2015

Sydney Corcoran, who suffered shrapnel wounds; and her mother, who lost both legs, said on Twitter: "My mother and I think that NOW he will go away and we will be able to move on. Justice. In his own words, 'an eye for an eye.'"

My heart is with our entire survivor community. I am thrilled with the verdict! #bostonstrong #bostonsafer — AdrianneHD (@AdrianneHaslet) May 15, 2015

Survivor Jarrod Clowery said he was happy not to have had to make the choice between life and death himself but he stands behind the jury's decision.

Liz Norden, whose two sons -- Paul Norden and J.P. Norden -- each had a leg amputated after the attacks, told reporters that the decision was bittersweet.

"There are no winners today but I feel justice for my family," she said. "I have to watch my two sons put a leg on every day ... but I can tell you it feels like a weight has been lifted off my shoulders."

Survivor Karen Brassard said, "I know there is still a long road ahead ... but right now it feels like we can take a breath ... Once the verdict came in it was like, 'Ok, we can start from here and go forward and really feel like it's behind us.' There's nothing happy about having to take somebody's life."

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U.S. Attorney Carmen Ortiz said the death sentence was the result of a fair and impartial trial.

"Even in the wake of horror or tragedy we are not intimidated by acts of terror or radical ideas," she said.

The bombings were not a religious crime, Ortiz said, even though the bombers claimed to represent Islam. It was a political crime committed by a pair of adults who adopted an ideology of hate, she said.

"It's time to turn the page in this chapter," Ortiz said.

Mayor Martin Walsh, in a statement, thanked the jurors.

"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," he said.

Completely numb... and waiting anxiously for the day this is really over. My heart and prayers are with my Boylston Street family. <3 — Rebekah Gregory (@rebekahmgregory) May 15, 2015

CNN Legal Analyst Jeffrey Toobin said a years-long appeal process is expected, but "the overwhelming likelihood is that he will die" as the sentence is eventually carried out.

Several of the survivors & family members dab tears from their eyes. Martin & Denise Richard did not want death. They look stoic. #Tsarnaev — Deborah Feyerick (@DebFeyerickCNN) May 15, 2015

The jury deliberated for more than 14 hours over parts of three days before reaching its sentencing decision. In the wake of Tsarnaev's conviction in April on all 30 charges against him, jurors were tasked with deciding whether Tsarnaev should be sentenced to life in prison or death.

The horrifying events of the attacks were relived in the Boston courtroom.

Jurors saw the second bomb go off by the Forum restaurant and they viewed videos and photographs of the carnage. They heard the screams and saw people on the street, dying even as bystanders rushed to help. And they heard from people who survived against all odds but continue to struggle with their injuries.

Rescuers spoke of the decisions they had to make in the face of such overwhelming bloodshed: Who could they save, and who should they leave behind?

The bombing of the finish line of the Boston Marathon, recalled other acts of terror on U.S. soil including the attacks of September 11, 2001. The homemade bombs, built with pressure cookers loaded with gunpowder, BBs and nails, also injured at least 240 people; 17 of them lost limbs.

Boston was on edge for days as the suspects remained at large. Finally, on April 18, police released surveillance images of two suspects they called "black hat" and "white hat." It didn't take long for the two to be identified as brothers Tamerlan and Dzhokhar Tsarnaev.

Within just a few hours of the release of the photos, a campus police officer at the Massachusetts Institute of Technology was shot to death as the fleeing brothers tried to take his gun. But they were thwarted by a locked safety holster.

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The Tsarnaevs hijacked a Mercedes SUV; Tamerlan told the driver he was responsible for the marathon bombing. The driver escaped when the brothers stopped at a convenience store for gas and snacks.

Tamerlan Tsarnaev, a 26-year-old married father and former Golden Gloves boxer, died hours later in a standoff with police in Watertown, a Boston suburb. Out of ammunition, he tossed his empty pistol at an officer and walked into a hail of police bullets. As officers wrestled him to the ground, Dzhokhar Tsarnaev ran at them in the stolen Mercedes SUV, running over his brother and dragging him.

The younger Tsarnaev was finally arrested the next day; he was discovered hiding in a tarp-covered pleasure boat in a Watertown backyard.

Dzhokhar Tsarnaev hid in the boat for hours. At some point, he picked up a pencil and wrote what prosecutors called his "boat manifesto." Streaks of blood covered portions of the writing and more than a dozen bullet holes obliterated parts of words.

It said he was "jealous" that his brother had achieved paradise by dying like a holy warrior during the gun battle with police. About the bombings, Tsarnaev wrote that he didn't enjoy killing innocents, but that circumstances called for it:

"The US Government is killing our innocent civilians but most of you already know that," he wrote. "Know you are fighting men who look into the barrel of your gun and see heaven, now how can you compete with that. We are promised victory and we will surely get it."

He wrote that he couldn't stand to see the U.S. government "go unpunished" for killing Muslims.

"We Muslims are one body, you hurt one you hurt us all."

He ended with: "Now I don't like killing innocent people it is forbidden in Islam but due to said [word lost to a bullet hole] it is allowed."

Laid-back terrorist?

In all, the trial consumed 59 court days. More than 150 witnesses testified over 10 weeks and hundreds of exhibits were shared with the jury.

All 12 of the original jurors stayed on the panel throughout the trial; no one asked to be excused. Only one day was lost due to a juror's illness.

Jury selection began during the first week in January, and 108 inches of snow fell in Boston before it was over. The first witnesses took the stand in early March, and Tsarnaev was found guilty in mid-April. The sentencing stage of the trial began on April 21.

Prosecutors focused their case on the stories of the dead and maimed, and of the brothers' social media activities and Internet exploration of radical jihad , including an al Qaeda online magazine article called "Build a Bomb in the Kitchen of Your Mom." It offered detailed instructions for how to construct pipe and pressure cooker bombs.

The defense sought to humanize Tsarnaev, turning its focus on his Russian immigrant family, and particularly on Tamerlan, the older of the two brothers. Defense attorney Judy Clarke said the crimes never would have been committed if not for Tamerlan.

The defense case featured testimony from former teachers, coaches and friends who found Dzhokhar Tsarnaev to be a laid-back, caring friend, industrious student and hard worker. As a youngster, he was academically gifted, overcoming the language barrier and skipping the fourth grade. His report card was studded with A grades.

Clarke emphasized Dzhokhar's youth and his quiet, "gentle" nature, despite growing up a neglected, "invisible child" in a chaotic family. He became untethered by his father's disabling slide into mental illness and his mother's embrace of religious extremism.

When their parents departed for Russia in 2012, Tamerlan became the dominant adult influence in Dzhokhar's life, she said.

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Clarke asked jurors to spare Tsarnaev's life, saying he is not beyond redemption. A vote for life, she said, is a vote for hope.

But she could not tell the jury the answer to the question that always has lingered over this trial: Why did he do it?

"If you expect me to have an answer, a simple clean answer as to how this could happen, I don't have it," she said.

Prosecutors said Tsarnaev sought to make a political statement. The bombing, Assistant U.S. Attorney Steve Mellin said, did exactly what it was meant to: It terrorized Boston and the rest of the country.

The trial highlighted the presence of Big Brother-style surveillance in matters public and private. The Tsarnaevs were visually identified from business surveillance videos of the marathon's finish line crowd. Jihadi material was retrieved from encrypted computer files, and investigators traced the purchase of the pressure cookers, fireworks, ammunition and an afternoon spent practicing at a New Hampshire shooting range.

Prosecutors cited surveillance video of Tsarnaev buying milk at a Whole Foods Market 20 minutes after the bombing and tweets such as "Ain't no love in the heart of the city" and "I'm a stress-free kind of guy" as evidence of his callousness.

Photos: Boston bomber Dzhokhar Tsarnaev Photos: Boston bomber Dzhokhar Tsarnaev Dzhokhar Tsarnaev was arrested on April 19, 2013, after a massive manhunt. An overnight shootout with police killed the other suspect -- Tsarnaev's 26-year-old brother, Tamerlan. A jury condemned Tsarnaev to death on Friday, May 15, for his role in killing four people and wounding hundreds more. Hide Caption 1 of 11 Photos: Boston bomber Dzhokhar Tsarnaev On April 18, 2013, the FBI released photos and videos of two suspects and asked the public to help identify them. Hide Caption 2 of 11 Photos: Boston bomber Dzhokhar Tsarnaev Dzhokhar Tsarnaev was found on April 19, 2013, in a boat that was dry-docked in the backyard of a Watertown home. He was covered in blood from bullet wounds. Hide Caption 3 of 11 Photos: Boston bomber Dzhokhar Tsarnaev The August 2013 cover of Rolling Stone featured Tsarnaev and sparked a backlash against the magazine. Hide Caption 4 of 11 Photos: Boston bomber Dzhokhar Tsarnaev Tsarnaev stands in court, flanked by his lawyers, in this sketch from July 2013. Hide Caption 5 of 11 Photos: Boston bomber Dzhokhar Tsarnaev An image posted to the social sharing website Reddit purportedly shows Dzhokhar Tsarnaev being detained by law enforcement officers. Hide Caption 6 of 11 Photos: Boston bomber Dzhokhar Tsarnaev Tsarnaev was seen on this convenience store surveillance video that was released by the Boston Police Department. Hide Caption 7 of 11 Photos: Boston bomber Dzhokhar Tsarnaev A still of the suspects from footage released by the FBI after the bombing. Hide Caption 8 of 11 Photos: Boston bomber Dzhokhar Tsarnaev Additional photos and video were released by the FBI. Hide Caption 9 of 11 Photos: Boston bomber Dzhokhar Tsarnaev A picture of Tsarnaev from his apparent profile on VKontakte, a Russian social network similar to Facebook. Hide Caption 10 of 11 Photos: Boston bomber Dzhokhar Tsarnaev The Boston Police Department also released this undated photograph of Tsarnaev. Hide Caption 11 of 11

Investigators were able to retrieve Dzhokhar's backpack, taken by friends from his dorm room, from a landfill. Inside, they found gunpowder residue and hollowed-out fireworks.

Tsarnaev also obtained a 9mm semiautomatic pistol from a friend; the gun was used to shoot MIT police Officer Sean Collier between the eyes as he sat in his patrol car on the night of April 18. Prosecutors called the shooting "an ambush" and said the brothers were after Collier's service weapon as they attempted to escape.

Another surveillance camera caught two men running from the shooting; a flash can be seen, the brake lights of Collier's squad car flicker on, then off, then on again. A passing bicyclist was later identified; he pointed out Dzhokhar Tsarnaev in court as the young man he saw leaning into the patrol car.

The killing of a police officer was, by itself, enough for prosecutors to seek the death penalty. But it came in the aftermath of the main event -- the bombing of the Boston Marathon.

The videos and photographs of the bloody mayhem that exploded near the finish line shortly before 3 p.m. on April 15, 2013, were difficult to watch and impossible to forget.

'This is messed up'

The stories of those killed and maimed were dramatic and haunting. Among them:

• Smoke coming out of Krystle Campbell's mouth as she screamed. The 29-year-old restaurant manager clutched her best friend's hand, said her legs hurt and then bled to death in the street. It took all of a minute.

• Lingzi Lu screaming in horror and agony as she covered her eyes with her long, tapered musician's fingers. The 23-year-old grad student vomited repeatedly as she bled to death. A police officer stood vigil by her side, even after being ordered to leave her body behind at the crime scene. The officer said she didn't want Lu to be alone.

• Denise Richard, blinded in one eye by bomb shrapnel, crouching over the shredded, 70-pound body of her 8-year-old boy, Martin, begging him to live: "Please, Martin, please!" Her husband, Bill, faced a difficult choice: Stay, or run to save their daughter? He scooped up 6-year-old Jane, her leg gone, and carried her to safety.

• Sydney Corcoran telling jurors what it felt like to slip toward death:

"I was dying. The blood was leaving my body. I was bleeding out. I remember thinking that this was it, I'm going to die, I'm not going to make it. And I remember feeling like I was just going to sleep. And it just felt so cold, and I almost felt peaceful because I just felt like I was going to sleep and I knew I was fading fast."

Photos: Boston bombing: The dead and injured Photos: Boston bombing: The dead and injured Martin Richard, 8, was in the second grade and loved the Red Sox. He was the middle of three children and is best known for a school project in which he made a poster with a peace sign and the words "No more hurting people." He was less than 4 feet from the second bomb. He bled to death as his mother leaned over him, begging him to live. Hide Caption 1 of 20 Photos: Boston bombing: The dead and injured Lingzi Lu, 23, was a graduate student from China, studying statistics. A gifted musician and public speaker, she was enjoying her time in the United States. She decided to watch the Boston Marathon as a study break. The second bomb sliced her leg open from hip to toe, and she bled to death. Her aunt called her "a beautiful nerd." Hide Caption 2 of 20 Photos: Boston bombing: The dead and injured Krystle Campbell, 29, was remembered by her father as his "Princess," but she loved sports and the outdoors and "wasn't a girly girl," he said. She put on big family parties and was close to her brother. She was working as a restaurant manager. She was burned and cut by hot shrapnel from the first bomb and bled to death. Hide Caption 3 of 20 Photos: Boston bombing: The dead and injured Sean Collier, 26, grew up in a big "Brady Bunch"-blended family and always wanted to be a police officer. He viewed the world from a moral stance, and felt a strong sense of right and wrong. He loved to race cars with his brother and go on family vacations. He was shot to death in his patrol car on the MIT campus because the Tsarnaev brothers wanted his gun to use in their escape. Hide Caption 4 of 20 Photos: Boston bombing: The dead and injured Celeste Corcoran, left, and her daughter, Sydney Corcoran, recovered in the same hospital room. Doctors were able to save Sydney's leg, but Celeste lost both of hers. Sydney recalled how she felt the life drain from her body and believed she was dying. Celeste felt great frustration when she couldn't rush to her daughter's side. "I never forget I'm a double amputee," Celeste said. "There's always a level of discomfort." Hide Caption 5 of 20 Photos: Boston bombing: The dead and injured Adrianne Haslet-Davis is a ballroom dancer. She remembers walking through the crowd on Boylston Street, holding hands with her husband, Adam, and feeling happy and in love. Then the bombs went off. Her husband, who is in the military, told her they'd been in a terrorist attack. But the second bomb went off before they could leave. She knew immediately something was wrong with her foot, and could see blood everywhere. She couldn't hear her own screams and thought she was dead. They were dragged into the Forum restaurant, and a first responder recalled hearing her husband apologize to her over and over for bringing her to the event. She testified that he recently checked himself into a Veterans Affairs mental health program. Hide Caption 6 of 20 Photos: Boston bombing: The dead and injured Erika Brannock was the last bomb survivor to leave the hospital. She came to the marathon from her home in suburban Maryland to cheer her mother on and was excited about being able to get so close to the finish line. Her sister, Nicole Gross, testified that she recalled pushing Brannock through the crowd so they could get closer. "I said, 'One, two, three, go,' and as soon as I said, 'Go,' the bomb went off," Gross said. Brannock told reporters in 2013 that she saw flashes of orange and yellow light and was knocked to the pavement. She couldn't move her foot and thought she was going to die. She said she's had moments when she was angry with the bombers but "I can't waste my energy being angry. I need to save energy for getting well and for being with people who care about me and want me to get better." Hide Caption 7 of 20 Photos: Boston bombing: The dead and injured Jeff Bauman remembers looking down at his legs. "It was just pure carnage. I could see my bones and the flesh sticking out, and I just went into tunnel vision. I thought this is really messed up, this is messed up, that's all I said in my head. This is how it's going to end. This is it. I had a great life. I saw the world. I played sports growing up. I had a lot of friends ... I made peace with myself at that point." Hide Caption 8 of 20 Photos: Boston bombing: The dead and injured Heather Abbott was outside the Forum restaurant when the second bomb went off. "I was catapulted through the doors of the restaurant, which was open. I landed in a puddle of chaos and blood and glass. People were running in herds by me, through the restaurant to get to the back exit, away from where the bomb was." Her foot was badly mangled, and she decided to amputate below the knee. She wears a prosthetic with toes and a high heel. Hide Caption 9 of 20 Photos: Boston bombing: The dead and injured J.P. Norden, left, and his brother, Paul Norden, did not testify during the trial, preferring to put the bombing behind them. Their mother, Liz, is outspoken in the survivor community. Hide Caption 10 of 20 Photos: Boston bombing: The dead and injured Karen Rand McWatters lost a leg -- and one of her best friends. She and Krystle Campbell spent the day laughing and posting selfies on Facebook before heading to the finish line. She was knocked to the ground by the first blast, and heard the second before she could understand what was happening. Her foot was turned in the wrong direction, but she dragged herself toward Campbell. She couldn't see how badly hurt her friend was. "I got close to her head, and we put our faces together. She very slowly said her legs hurt, and we held hands and very shortly after her hand went limp and we never spoke again." Hide Caption 11 of 20 Photos: Boston bombing: The dead and injured Mery Daniel, a young mother from Haiti, was attending her second marathon when she was knocked to the pavement. She lost a leg, and the other leg was also damaged. She had pushed herself from ESL classes all the way to medical school, and instead found herself relearning how to walk with a prosthesis. She wears her "Boston Strong" T-shirt proudly. Hide Caption 12 of 20 Photos: Boston bombing: The dead and injured Marc Fucarile was at the marathon with friends, and was struck by hot shrapnel from the second bomb. His pants caught fire, and he suffered burns over 90% of his lower body. His belt buckle was so hot, it burned his hand when he tried to undo it. One leg was blown off at the scene, and he's still trying to save the other, but might not win that battle, he said. He's had more skin grafts than he can remember. Hide Caption 13 of 20 Photos: Boston bombing: The dead and injured Patrick Downes and Jessica Kensky Downes met when they were interns on Capitol Hill. She lost both legs and was pushed into court in a wheelchair. Her aide dog, Rescue, lay beside her as she testified. "I remember being happy, I remember feeling sunlight on my face. I remember feeling free." And then the bomb went off. Because she is a nurse, she focused on saving her husband. His foot and part of his leg were hanging by a thread. She remembers screaming, and not being able to hear anything. This photo was taken before she decided to amputate her second leg in January. "I wanted to paint my toenails and put my feet in the sand. I wanted all of those things, and to lose my second leg was a gut-wrenching decision." Hide Caption 14 of 20 Photos: Boston bombing: The dead and injured Rebekah Gregory was celebrating her birthday weekend at the marathon with family and friends. She remembers coming to after the blast and reaching for her 5-year-old son, Noah. She could see bones protruding from her arm. She also lost a leg below the knee. Like many bomb survivors, she was convinced she was going to die that day. She is using a blade to run again. After she testified, she wrote a note to Dzhokhar Tsarnaev on her Facebook page saying she is not afraid of him. Hide Caption 15 of 20 Photos: Boston bombing: The dead and injured Roseann Sdoia had run a 5K the day before the marathon. She heard the first bomb and decided to run for it. Then she saw two explosions of white light at her feet. She knew she'd lost a leg before she hit the ground. She saw a severed foot with a sock and remembers asking herself if she wore socks that day. "It was somebody else's foot." She thought she'd rather die than live as an amputee but then considered all the people she'd be leaving behind. So she willed herself to stay conscious and fight. Hide Caption 16 of 20 Photos: Boston bombing: The dead and injured Jane Richard, in the pink skirt, lost her leg. She holds the hand of her brother Henry as they walk down Boylston Street with their parents and others after an April 15 ceremony this year. She was standing next to her brother Martin behind a metal barricade when the second bomb went off. Her father, Bill, took one look at Martin, knew he wouldn't make it and focused his efforts on saving Jane. She sang in April at Fenway Park on opening day. Hide Caption 17 of 20 Photos: Boston bombing: The dead and injured Mary Jo White and Bill White, right, had gone with son Kevin into the city for lunch and were on their way back to "the T," as Boston's public transportation system is called, when they decided to stop by the finish line. They were just feet away from the first bomb. Bill, a veteran who earned a Purple Heart in Vietnam, lost his leg above the knee. Kevin, who serves as the family spokesman, says his parents, who are in their 70s, don't like to talk about the events of April 15, 2013. He told his local newspaper he "really has no feelings" for Dzhokhar Tsarnaev. Hide Caption 18 of 20 Photos: Boston bombing: The dead and injured Steve Woolfenden, a biomedical researcher, was pushing his son, Leo, in a stroller along Boylston Street. His wife was running the marathon, and they were making their way to the finish line when the first bomb went off. He started to turn the stroller around in the crowd, but the second blast caught them. Woolfenden's leg was severed on the scene. He could see it still in the boot next to him, the tibia protruding. His focus was on Leo and getting him help. Hide Caption 19 of 20 Photos: Boston bombing: The dead and injured Leo Woolfenden was lifted from his stroller by a first responder as the boy's father lay on the ground with a severed leg. Leo suffered a skull fracture.

Hide Caption 20 of 20

• And Jeff Bauman describing his thoughts as he looked down at the place where his legs had been and saw a bloody bone protruding from the torn flesh: "This is messed up." He said he "knew instantly that my legs were gone."

In one of the trial's most dramatic moments, prosecutor Mellin paused during his closing for what turned out to be 20 seconds. He gained the attention of everyone in the courtroom as silence consumed them.

Twenty seconds. It seemed like forever. And then Mellin said: Multiply that pause by 12, and that's how long Tsarnaev stood with his backpack bomb behind a row of children.

He also brought home the continuing ripples of devastation, ticking off the names of the 17 people who lost limbs in the blast:

Jeff Bauman

Erika Brannock

Celeste Corcoran

Mery Daniel

Rebekah Gregory

Patrick Downes

Jessica Kensky

Karen McWatters

William White

Heather Abbott

Roseann Sdoia

Marc Fucarile

Paul Norden

J.P. Norden

Adrianne Haslet-Davis

Steve Woolfenden

Jane Richard

For them, and for the families of Krystle Campbell, Martin Richard, Lingzi Lu and Sean Collier, this case will never be over.