Anguish and anger palpable at first of 31 funerals for victims of El Paso and Dayton massacres

Sorrow and outrage overwhelmed mourners gathered in Ciudad Juarez, Mexico, to welcome home and bid farewell to a beloved school principal who was one of the 22 people killed while shopping at a Walmart in El Paso, Texas.

The funeral Wednesday for 57-year-old Elsa Mendoza de la Mora was the first for the victims slain in mass shootings in El Paso and Dayton, Ohio, that occurred on consecutive days over the weekend and sent shock waves across the United States and Mexico, prompting new calls for action to stop gun violence.

"Personally, I am very outraged because this is unfair for her and for the other people that died. They did not deserve this," Alma Vargas Marquez told Telemundo TV network outside the funeral home where her cousin Mendoza de la Mora's funeral occurred.

Mendoza de la Mora's body arrived in Ciudad Juarez in a black Cadillac hearse that was escorted by motorcycle police on the 7-mile journey across the southern border from El Paso.

Marquez and other mourners were already gathered outside the funeral home when the hearse pulled up and pallbearers dressed in black suits carried a gray casket bearing the body of Mendoza de la Mora inside.

Another cousin of the slain woman, Ruth Vargas Marquez, said she wishes the deaths of the 31 people killed in both massacres will finally be a "call to consciousness."

"This is the moment that we leave behind hatred, racism, fear and do things differently and unite," Ruth Vargas Marquez told Telemundo. "I think the message of Elsa is to keep loving each other and make things different."

Mendoza de la Mora was a mother of two children and a special education teacher and principal of the Rafael Veloz Elementary School in Ciudad Juarez, relatives said. Her husband, Antonio de la Mora, described her as "the most wonderful of women" in a Facebook post.

She was inside the Walmart shopping when alleged gunman Patrick Crusius, 21, walked through the front door about 10:30 a.m. Saturday firing an AK-47-style rifle, investigators said. Her husband and son were waiting for her in a car in the parking lot when the gunfire erupted, authorities and relatives told reporters.

On Thursday afternoon, another funeral was held in Ciudad Juarez for Ivan Manzano, the 41-year-old father of two who was also killed in the mass shooting in El Paso. Manzano was the owner of a business that supplies orthopedic implants.

Among the mourners at Manzano's funeral was U.S. presidential candidate Beto O'Rourke, a former Democratic congressman from El Paso. O'Rourke told reporters he was invited to the funeral by Manzano's family.

O'Rourke said he crossed the border not only to express his condolences to Manzano's family but "to remind the world that we are a binational community."

"The only way to truly demonstrate how closely knit these communities are is for me to walk over and be with those who have suffered and to give my condolences to the people of Juarez in Ciudad Juarez," O'Rourke told reporters outside the funeral chapel. "This feels like the right thing to do and it feels very much like what we've always done in this binational community. So, I'm grateful that I get the chance to do that."

In addition to the 22 people killed in El Paso, more than two dozen were injured.

The volunteer group Operation H.O.P.E. (Helping Other People Endure), which provides clothing, shoes and even food for the needy in the city, has volunteered to cover the funeral expenses of all the victims in the Walmart shooting.

Following his arrest, Crusius told investigators he was bent on killing as many Mexicans as possible and authorities suspect he is the author of an anti-immigrant screed posted on the controversial online message board 8chan just before the attack.

The mass shooting came a day before nine people were killed when a gunman went on a killing rampage in Dayton, Ohio.

Memorial services for the victims in both shootings are scheduled to continue through the weekend and into next week.

Earlier this week, 15-year-old Javier Rodriguez, the youngest victim killed in the El Paso shooting, was mourned by his teachers and classmates at Horizon High School in El Paso.

"Javier was just a young man full of life, running in this same stadium we're in now," Juan Martinez, superintendent of the Clint Independent School District, said at the vigil, held on the football field at the school. "He didn't deserve to die in a tragedy like this."

ABC News' Wil Gretsky contributed to this report.