/ Updated 
By Arturo Conde

One Mexican woman says that justice for some human rights issues can best be pushed through the conviction, determination and love of a mother.

“Even though we are farmers and we come from indigenous villages, we have to demand that the government return our children alive,” said Cristina Bautista Salvador, the mother of Benjamín Ascencio Bautista, one of the 43 teacher’s college students who disappeared in Mexico over 19 months ago. She is still holding out hope her son is alive and she will be able to see him again.

Cristina Bautista, mother of Benjamin Ascencio, one of 43 missing students, participates in march in Tixtla, Guerrero State, Mexico, on November 13, 2014.AFP/Getty Images

The Ayotzinapa families maintain that their sons are still being held captive by Mexican police and military. A recent report by the Inter-American Commission on Human Rights challenges the Mexican government’s investigation—which concluded that the students were murdered by a drug gang and later incinerated in a garbage dump—pointing to evidence that key suspects in the case had been tortured for testimonies.

“With the report from the forensic experts the government can no longer say that it knows nothing,” said Bautista. “We have scientific evidence that proves that police forces were involved. And we need to keep fighting for our sons.”

Speaking by phone to NBC Latino, Bautista said that her son Benjamín—who turned 21 years old on April 9—wanted to become a teacher so that he could take care of his family. He aspired for a fulfilling life where neither he nor his mom had to do more backbreaking labor.

“He told me that he did not want to work like a donkey,” she remembered. “He wanted to work like an ox. An ox works with his horns. And a donkey works with his back. My son wanted to work with his head.”

A portrait of Benjamin Ascencio Bautista, one of the missing students , is hung on a Christmas tree decorated with pictures of 43 missing students from the Isidro Burgos rural teachers college in Iguala, Guerrero, Mexico on December 21, 2014.Anadolu Agency / Getty Images

The Mexican mother explained that she had worked hard most of her life like a “burra” (donkey), raising Benjamin and his two sisters by herself—the father abandoned the family in 1999.

Bautista immigrated to the United States in 2000 to earn money for her children. She started out at a carwash, but later switched to fast-food chains like McDonalds and Burger King, where she worked 15-hour days, 7 days a week, until she saved enough money to go back to Mexico and build a house for her family.

Now, Bautista says that her son has taught her a valuable lesson. And she pushes forward like an ox, yoked together with the families of the missing students, to strengthen her quest for Benjamin.

Bautista says she has to push others when they are feeling discouraged by the lack of answers, and the grief. “As mothers we have to go out and tell the truth. We have to take action to bring people together.

"If we stay home with our arms crossed, crying, we will never know anything,” said the mother.

Cristina Bautista, mother of Benjamin Ascencio, one of 43 missing students, walks inside the Raul Isidro Burgos de Ayotzinapa school minutes before departing in a caravan of students and relatives of the missing students heading for different parts of the country, in Ayotzinapa, near Tixtla, Guerrero State, Mexico, on November 13, 2014.AFP/Getty Images

For Bautista, there is no greater conviction than the determination of a mother, or father, to find her son. And the love she feels for Benjamin has made her tireless.

“We have to be stronger than ever,” she said. “Mobilize more. Prove that we love our children. Prove that we will not give up and that we have much more strength.”

The Ayotzinapa parents have been marching, fasting, and even chained themselves to the Ministry of Interior building in Mexico City to demand that the government keep the investigation for their sons’ case open. They will meet this Saturday to plan more actions.

Follow NBC News Latino on Facebook, Twitter and Instagram.