Ajima, who asked that her surname be withheld for privacy reasons, told AFP she was a relative of the boy and felt deeply sorry for him.
„A boy at that age is like a blank piece of fabric. He must have gone through a lot of issues, but nobody knows why he resorted to shooting as a solution. I feel terribly sorry for him,“ she said.
Investigators are still seeking a motive for the shooting, but police said on Sunday the boy had watched violent videos online and once brought a BB gun to school.
Officials said previously that he faced academic-related stress, and a classmate said he was bullied.
„I feel really sorry for the boy,“ said Somjai Poosod, whose grandchildren attend the school attacked, one of whom was a friend of the shooter.
„Of course I feel bad for the innocent people who were killed, but I feel there is an issue of mental health that we may need to address to prevent incidents like this from happening again,“ she added.
The shooter, who AFP is choosing not to name, used his grandfather’s gun to kill his grandparents before heading to the school.
There, he shot dead five teachers and staff and wounded a 12-year-old girl, who died in hospital on Saturday.
Thailand has one of the highest rates of gun ownership in the region, and past promises of tightening gun laws have not prevented repeated shootings.