EL PERICON, Mexico — The blur of scientific talk from the investigators washed over him — something about a bone fragment, DNA testing, probability — as he sat dazed in an abandoned classroom at the teachers college his son attended.

But Ezequiel Mora — who, like other parents of the college’s missing students, had been waiting weeks for word of their children — wanted to know only one thing: Was his son Alexander, a 19-year-old who had sought escape from the farming life to become a teacher, dead or not?

“I stopped them and asked them to give it to me straight,” he said Sunday at his home here, referring to his meeting late Friday with Argentine forensics experts working with Mexico on the case of 43 students missing since September. “Then they told me it was my son, and that he was dead.”

He added: “They punched me in the heart. I wanted to scream.”

He asked for and received a shot of mezcal for comfort.

The news that the first of the students had been confirmed as dead rocked not only Mr. Mora but much of Mexico, where many have been consumed by the fates of the students and, in march after march, demanding that the government end the country’s widespread lawlessness and corruption.

Now, it seems highly likely that the other missing students are dead, too.

On Sunday, Attorney General Jesús Murillo Karam confirmed that a laboratory in Austria had matched a bone fragment found among charred remains to Alexander Mora’s DNA. The result provides strong evidence for the theory that the students were killed and burned to ashes. Witnesses have told investigators that the local police abducted the students and turned them over to a gang on behalf of a corrupt mayor in conflict with them.

Mr. Murillo Karam said 80 people had been arrested in the case so far and that 16 more were being sought.

President Enrique Peña Nieto, who is suffering the worst crisis in his two-year term, has promised justice and unveiled a series of changes that would disband most municipal police forces and place them under the control of the states.

But here in Alexander’s hometown, one that has wrestled greatly with crime, people lashed out at a government they viewed as corrupt and inept while mourning a young man, who like many classmates, saw the teachers college as the only viable way to get ahead. He studied at another university for a short time, with the idea of becoming a lawyer, but settled on teaching.

As many as eight other missing students come from this region of Guerrero State, one of the poorest and most violent in Mexico.

For many boys aspiring to lives away from the fields of squash and jicama, the teachers college in Ayotzinapa, about an hour’s drive from Acapulco, provides one of the more viable alternatives.

Alexander had just started there a few months before he was abducted with other students in a confrontation with the police in Iguala; the students had sought to steal buses for a coming demonstration, a common practice.

Mr. Mora last spoke to his son on Sept. 16, when Alexander came home to celebrate Mexican Independence Day, but they talked on the phone a few times after that, as Alexander requested money for meals.

In this dusty town of 2,000, neighbors and family members, several weeping, streamed into the small, two-bedroom cinder-block house as Mr. Mora built an altar in the living room with flowers and pictures of Alexander.

Mr. Mora patiently greeted them for hours, but at one point retreated to a back room, where he could be heard sobbing.

“You have to be strong, for the rest of those poor students,” a woman said as she consoled him. “You can’t give up now; something has to change.”

Mr. Mora said he had nothing but contempt for the country’s leaders and did not know what to believe about the apparent motive for the killings. He noted bitterly that none of the country’s leaders had called him to express condolences.

“Government lies — that is all they do,” he said. “They never give us complete answers about investigations, about missing people or murders.”

Even in this remote town, a wave of kidnappings and street crime prompted people to set up their own “community police force,” with grudging recognition from the state authorities.

Overwhelmed with grief, Mr. Mora said he accepted the findings of the DNA test because they were supported by a team of Argentine forensic investigators working with the government at the request of human rights officials.

Mourners here recalled Alexander as a quiet, polite youth who loved sports, especially soccer, which he played every afternoon. His mother died five years ago of diabetes, leaving Mr. Mora to raise him and seven other children. Alexander’s respectful manner attracted girls, said family members and friends.

“He was the only one of my older brothers that used to give me advice, instead of scolding me,” his sister Saena said. “He was like a friend, not just a brother. His girlfriends used to tell me, ‘What a gentleman.’ ”

Alexander joked about his charm, she said, once saying, “I might be ugly, but it’s my personality that wins them over.”

Mr. Mora said he had barely slept and barely cried, too overwhelmed with the news and visits. Still, family members said they were taking comfort from the community, with several residents squeezing into Mr. Mora’s home on Sunday evening for a prayer vigil.

“Maybe because I haven’t been able to cry all that much I have this terrible headache,” he said.

He was told he would receive the remains in a couple of weeks.

“I just want to wait for his little bones,” he said.

“I just hoped they would have killed him and left the body somewhere along a road for someone to find him and bring him to me,” he said. “That way you can find some kind of comfort.”

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Paulina Villegas reported from El Pericon and Randal C. Archibold from Mexico City.