In the border town of El Paso, Texas, a shooter opened fire and left 20 people dead and more than two dozen injured. Hours later in Dayton, Ohio, a shooter killed 9 people and injured at least 27 others.
Here are some of their stories.
Jordan Anchondo: 'Gave her life' for her baby
Jordan Anchondo was among those killed in El Paso, Anchondo's sister said, and she apparently died while protecting her 2-month-old son from the hail of bullets.
Leta Jamrowski, of El Paso, spoke to the Associated Press as she paced a waiting room at the University Medical Center of El Paso, where her 2-month-old nephew was being treated for broken bones - the result of his mother's fall.
"From the baby's injuries, they said that more than likely my sister was trying to shield him," she said. "So when she got shot she was holding him and she fell on him, so that's why he broke some of his bones. So he pretty much lived because she gave her life."
Jordan, a mother of three, and Andre Anchondo had dropped off their 5-year old daughter at cheerleading practice before going to shop for school supplies Saturday at a Walmart in El Paso. They never returned.
Andre Anchondo remained unaccounted for. Bodies of victims were still in the Walmart on Sunday.
Nicholas Cumer: Had helped cancer patients
A graduate student at a university in Pennsylvania who was interning with a Dayton facility for people battling cancer was among those killed in the Ohio city early Sunday.
Nicholas Cumer was a graduate student in the master of cancer care program at Saint Francis University.
"Nicholas was dedicated to caring for others," university President Malachi Van Tassell said in a statement. The university, in Loretto, Pennsylvania, is the oldest Franciscan institution of higher learning in the United States.
Cumer had been in Dayton as part of his internship program with the Maple Tree Cancer Alliance, which strives to improve the quality of life for individuals battling cancer through exercise, nutrition and faith.
Lois Oglesby: A nursing students who wanted to care for children
Lois Oglesby, 27, was in nursing school and looked forward to a career that would make the most of her love for children, her cousin said. She was also the mother of a newborn and had an older daughter.
Derasha Merrett told the Dayton Daily News that she was up feeding her own newborn when a friend called her at 3 a.m. Sunday to tell her that Oglesby had died in the Dayton shooting.
"She was a wonderful mother, a wonderful person," Merrett said.
Merrett said she and her cousin grew up in the same church, were on the same drill team, and Oglesby worked at her children's day care center.
"We all grew up in this little town," Merrett said. "We're all family."
Jessica Coca Garcia and Memo Garcia: Fundraising for kids' sports team
Jessica Coca Garcia and Memo Garcia were at the Walmart in El Paso to raise funds for a youth sports team one of their children played on when a gunman opened fire, wounding them, a relative said.
Norma Coca told Wichita, Kansas-television station KWCH that her daughter and son-in-law were near the front doors of the Walmart when they were shot.
Coca, who lives in Salina, Kansas, said her daughter, Jessica Coca Garcia, was shot three times in the leg. She said her son-in-law, Memo Garcia, was shot twice in the leg and once in the back. Her daughter was in stable condition, and her son-in-law was in critical condition.
Jessica Coca Garcia's father, Don Coca, said: "She was just crying. I told her that our prayers are there, and we're on our way."
The couple's 5-year-old son and 11-year-old daughter were also at the Walmart and were not shot.
Mario de Alba: A wounded father
Mario de Alba, 45, had come to El Paso with his family from Mexico to go shopping.
Described by his sister, Cristina de Alba, as an "excellent father" and a "decent, hardworking person," he was in serious condition Sunday after being shot in the back, the bullet exiting via his diaphragm.
His wife, Olivia Mariscal, and 10-year-old daughter, Erika, appear to be recovering after also being wounded, de Alba said from the El Paso hospital where her brother is being treated.
The family lives in Chihuahua, Mexico - a four-hour drive south of El Paso - and was buying school supplies in the Texas city. El Paso is a popular shopping destination for people who live in northern Mexico.