Police have arrested the grandfather of the 11-year-old boy who murdered his schoolteacher and injured six others before shooting himself dead.
The arrest occurred hours after state officials in the Mexican province of Coahuila said the guns used in the attack belonged to Jose Angel Ramos' grandfather.
State prosecutors said he was being held in prison in the city of Torreon, where last Friday morning's shooting took place, on suspicion of homicide by omission.
The 58-year-old, who has not been fully named, has been warned he could face a prison sentence of up to 35 years if convicted.
File photo of Miguel Cervantes School in Torreón where a pupil shot dead his teacher before killing himself Friday
Shocking photos from the scene showed the student's body next to that of his female teacher with a handgun on the floor between the boy's knees
María Medina, a teacher at private school in Mexico, was killed by one of her students. She confronted José Ángel Ramos, who was holding two guns, after the boy had asked her for permission to go to the bathroom to change his pants. A parent lauded her actions and said Medina's heroic actions prevented the tragedy from being worse
State General Attorney General Marquez Guevara, confirming the arrest, said: 'We are accusing him in some way of the homicide of the teacher who lost her life, on the basis there was omission in his negligence in having firearms in a private home where a minor was living.
'The information we have is that the grandfather was the reference, the person who was in charge of the home.'
Coahuila state governor Miguel Angel Riquelme said after the private school shooting at Colegio Cervantes in Torreon, a city of just under 700,000 inhabitants in north-east Mexico, that Ramos could have been influenced by a video game called Natural Selection.
It subsequently emerged the child gunman was dressed in the same clothes worn by Eric Harris when he murdered 12 students and one teacher with Dylan Klebold at Columbine High School on April 20, 1999.
José Ángel Ramos (pictured in the left image), the 11-year-old boy who shot dead a teacher and then killed himself at a school in Mexico , appeared to be dressed in the same clothes that Eric Harris, one of the teen killers, wore in the Columbine 1999 massacre. Harris (pictured left in the right image) was portrayed in the documentary film 'Zero Hour'
Paramedics carry one of the injured victims out of the school in Torreon, Mexico
The Torreon shooting occurred when Ramos' teacher Maria Assaf Medina went to look for him after he asked for permission to go to to the toilet and failed to return 15 minutes later.
The school teacher was laid to rest on Sunday.
Initial reports after the shooting pointed to the gunman being just eight before city mayor Jorge Zermeno confirmed he was a sixth-form primary school pupil aged 11.
Five pupils and another teacher, 40-year-old PE teacher Aldo Omar Saldivar, were wounded. Most of the injured have already been released from hospital.
In the aftermath of the shooting local authorities said Ramos had not shown any outward signs of any problems, but investigators are now pointing to behaviour influenced by an 'absence of values and lack of attention.'