FORT HOOD, Texas (AP) - One of Angela Rivera's saving graces after her husband was gunned down at Fort Hood was his voicemail greeting. For years after Maj. Eduardo Caraveo was killed in 2009, Rivera had his cellphone kept active so she could call it and hear his voice telling her to leave a message. Then, one day, it disappeared when the cellphone carrier upgraded its systems and required users to tape a new greeting. Rivera was among a dozen widows and soldiers who provided a picture of overwhelming grief and attempts at recovery, as military prosecutors began to try to persuade a jury that Maj. Nidal Hasan deserves a death sentence. As many as seven more people will get their chance Tuesday to tell jurors how Hasan changed their lives forever. Witnesses recalled the litany of moments, large and small, that remind them of what they lost: a voicemail greeting, a box of photos or the thought of a daughter's lonely walk down the aisle one day. The jury of 13 military officers must be unanimous to condemn Hasan. Prosecutors will try to prove an aggravating factor - one possible factor under military law is the killing of multiple people - and present evidence to show the severity of Hasan's rampage at a medical building on this Texas Army post nearly four years ago. Many of those who testified Monday talked about their biggest fear in the long hours after the shooting in the early afternoon of Nov. 5, 2009: the appearance of two soldiers at their doorstep, meaning their husband, parent or child was dead. Some said they waited more than 12 hours after Hasan shouted "Allahu Akbar!" and opened fire on unarmed soldiers. They tried in vain to call whatever phone numbers they could find. Rivera described driving to the airport immediately after the shooting to pick up relatives. Her young son, John Paul, saw the airport and wondered if they were going to get his father. "Ms. Rivera, how do you explain to a 2-year-old the concept of death?" asked Col. Mike Mulligan, the lead prosecutor. "I couldn't do it," Rivera replied, adding that a therapist later helped her explain what happened. Rivera identified her husband's former cellphone carrier as Sprint. A spokeswoman for Sprint did not return messages Monday afternoon about the voicemail greeting. When Cindy Seager heard initial reports of a shooting at Fort Hood, she drove home hoping that she wouldn't see an unexpected car on her street. There wasn't one when she arrived. But two officers came to her door at around 1 a.m., about 12 hours after the shooting. Her husband, Capt. Russell Seager, was dead. "I'd known him for 30 years," Cindy Seager said. I had to learn to be independent again, find things to do. It's getting better, but it's difficult. Shoua Her wiped away tears as recalled how she and her husband, Pfc. Kham Xiong, talked about growing old together and having more children. Now, she said, her children know their slain father only through memories or stories. The 21-year-old was pregnant when she was shot, and her cries of "My baby! My baby!" during the attack were described by several trial witnesses. He killed my grandson (Velez' unborn child) and myself," Velez said in Spanish. Prosecutors have seven witnesses left to call. Testimony Monday afternoon was abruptly canceled after a closed-door meeting between the judge, Hasan and attorneys on both sides. Officials said the delay was related to logistics. The sentencing phase also will be Hasan's last chance to tell jurors what he's spent the last four years telling the military, judges and journalists: that he believes the killing of unarmed American soldiers preparing to deploy to Iraq and Afghanistan was necessary to protect Muslim insurgents. Whether he plans to speak, however, remains unclear. Hasan continued to show little reaction Monday. He questioned none of the 12 prosecution witnesses, though he appeared to look down briefly and close his eyes during the testimony of one widow. He is representing himself during his trial, yet he called no witnesses, declined to testify and questioned only three of prosecutors' nearly 90 witnesses before he was convicted last week. The president must eventually approve a military death sentence.