Joaquin Oliver’s mother can’t bear to go with relatives for family celebrations because her son is gone. Jaime Guttenberg’s mother has a hard time watching her beloved Florida Gators play football, because it was also her daughter’s favorite team. Gina Modalto’s father struggles with his marriage, troubled by grief over the loss of his daughter. One by one, relatives and friends of the 17 people killed at Marjory Stoneman Douglas High School in Parkland, Florida, took the stand this week and revealed in court the depths of their despair since losing loved ones to a shooting for four years before Valentine’s Day. In four days of deeply emotional testimony, they shared painful and intimate details that revealed how their inner lives remain shattered and how massacres like Parkland leave families with years of unresolved grief. “I have a box over my heart with a lid so tightly closed, trying to keep all my emotions under control,” said Linda Beigel Schulman, who lost her son, Scott J. Beigel, a geography professor. “But today, I’m taking the lid off that box.” Shocking testimony concluded Thursday after the jury that decided the fate of the gunman, Nikolas Cruz, toured the school building where the mass shooting took place. Prosecutors gave up viewing the crime scene, an extremely rare and visceral occurrence in a criminal trial, for the final day of their nearly three-week presentation and rested their case. What the 12 jurors and 10 alternates saw inside Stoneman Douglas High’s Building 12, which had been cordoned off and unused since the day of the shooting, was a moment frozen in time, a joyous celebration interrupted by a deadly rampage. Bullet holes pierced the doors and walls. Shards of shattered glass crunched under their feet. Laptops remained open, classroom work unfinished. Dried rose petals were scattered on blood-stained floors. In an unfinished English class assignment, one student had written: “We go to school every day of the week and take everything for granted. We cry and complain without knowing how lucky we are to be able to learn.” A second-floor hallway had a James Dean quote: “Dream like you’re going to live forever, live like you’re going to die today.” The crime scene visit capped 12 days of often gruesome video and autopsy evidence in a tense trial in which the jury will decide whether Mr. Cruz, 23, who pleaded guilty, should be sentenced to death or life in prison without parole. the possibility of parole. The defense is scheduled to open its case on August 22. The judge will first hold a non-jury hearing to decide whether defense lawyers can use a map of Mr. Cruz’s brain as evidence of the effects of fetal alcohol syndrome. Before hearing from the victims’ families and relatives, the jury heard 17 survivors who were injured in the shooting recount how they suffered their injuries and what lingering effects were left by the high-velocity shooting. Several still have pieces of shrapnel in their bodies. Benjamin Wikander’s radial nerve was so badly damaged that he still has to wear an arm brace. Maddy Wilford struggles to breathe with her right lung. Sam Fuentes suffers from chronic pain and spasms in her legs and no longer has the range of motion she once had. But the courtroom felt perhaps more somber, as parents, siblings, grandparents and friends struggled to stay calm while remembering their loved ones and describing life without them. They often reached for tissues. A bailiff offered them water. “I can do this,” said Tori Gonzalez, Joaquin Oliver’s girlfriend, as she took deep breaths on the witness stand. A juror cried as she called Joaquin her soulmate. “I lost my innocence,” he said of the shooting. “I lost my purity. I missed the love letters he wrote about me in that fourth period creative writing class.’ Many relatives spoke of being unable to celebrate birthdays and holidays after the shooting. Peter Wang’s family no longer gathers for Chinese New Year. Luke Hoyer’s mother described Christmas as almost unbearable. Helena Ramsay was killed on her father’s birthday. Families mourned that they would never see their children graduate from high school or college. Never take them down the aisle. Never be glad they have kids of their own. “She never took her braces off,” said Meghan Petty, Alaina Petty’s sister. “She never got her first kiss.” Parents and spouses described their homes as unbearably quiet. “The night no longer brings familiarity and comfort,” said Debra Hixon, the wife of Chris Hixon, the school’s athletic director, “just the intensity of silence.” Her son Corey Hixon, who has Kabuki syndrome, a rare genetic disorder, said simply of his father: “I miss him!” Some people were angry. Alyssa Alhadeff’s father, Dr. Ilan Alhadeff, cried repeatedly through tears: “This is not normal!” He said his wife “occasionally sprays Alyssa’s perfume to try to smell her.” “He even sleeps with Alyssa’s blanket, four years later,” she added. Some parents find it difficult to work. Fred Guttenberg, the father of Jaime Guttenberg, who became a gun control activist, said he was unable to hold down a regular job and that his public crusade “made life harder for my wife and my son , and for that I am sorry.” “That broke me,” he said. The shooting changed his relationship with his son, who was supposed to be waiting for Jaime and walking her home after school that day. Instead, as soon as Mr. Guttenberg learned of the shooting, he told his son to run. “He’s struggling with the reality that he couldn’t save his sister and wishes it was him,” she said. “He’s angry that I made him run.” As victim after victim spoke, many people in the courtroom wept. So are several defense attorneys. Nicholas Bogel-Burroughs contributed reporting.