Night has become the most difficult time for the parents of 43 students from a rural teachers college who disappeared a month ago.

Sleep has eluded Clemente Rodriguez Moreno, 46, since his 19-year-old son, Christian, disappeared with his classmates. Each night Rodriguez returns to his home close to the Raul Isidro Burgos school in Tixtla, and his mind races.

"What will come of them?" Moreno said. "We don't know if he's eating, if he's injured, if they're hitting him."

The lives of the families have been thrown into turmoil since police in the town of Iguala, allegedly on the mayor's orders, attacked the students to stop them from interrupting a speech by the mayor's wife on Sept 26. Both the mayor and his wife are fugitives, along with the police chief.

Three students, including one later found with the skin peeled off his face, and three people unrelated to the attack died in a series of initial attacks.

Investigators say the rest of the students were driven off to a police station and later turned over to the drug gang Guerreros Unidos. They have not been heard from since.

It has been a nightmare, said a 57-year-old farmer from Ayutla who spoke on condition of anonymity as a precaution against reprisals. He walks his 19-year-old son's campus in the Ayotzinapa neighborhood in a daze.

"I don't sleep for the thinking," he said, fingering a foil packet of sleeping pills prescribed by a doctor. "I don't feel like I'm living life."

His family has few resources, he said, and his son came to the school because the students support themselves. That's what he said they were doing that afternoon in Iguala, soliciting donations.

Staring at the photograph of his son after a march to demand the return of the missing, the farmer spoke one moment of the anguish of not knowing. His eyes welled with tears and he bit his lower lip. Next he flashed an anger that has been building over weeks. He said he's tired of a corrupt government that has always scorned poor farmers. He wants the guilty to pay.

"If they don't give them to us, we'll have to proceed another way, with more resistance," he said.

There was so much confusion in those early days, said Valentin Cornelio Gonzalez, a 30-year old farmer from the municipality of Tecoanapa who dropped everything to travel to the school, where his brother-in-law, 19-year-old Abel Garcia Hernandez, is enrolled.

Was the attack at the school or in Iguala? Were the attackers police or cartel gunmen? How many students were missing?

Some of those questions have been answered. But the major one, the one families care most about, is still unanswered despite the arrest and interrogation of more than 50 suspects.

So Gonzalez, clad in well-worn leather sandals, has been marching in the state capital of Chilpancingo, in Acapulco, in Mexico City, demanding an answer.

When he first arrived at the school, he and other relatives spent a fruitless day searching around Iguala. They feared for their safety, but blame the government for not doing enough.

"They're not looking for them as they should," he said.