On Friday morning, as the final classes of the week were under way, panicked students began streaming out of a prestigious school just outside Bangkok.

Inside, police say, a 14-year-old boy had opened fire.

"I was standing in front of the teacher when she was shot," a shaken seventh grader tells the BBC, near the gates of Debsirin School in Nonthaburi. "She was talking to me when [the gunman] showed up."

Still in her uniform, with her mother by her side, she explains how the shooter stalked from room to room.

Authorities say he killed five teachers and injured more than 30 people - including fellow pupils - before turning the weapon on himself. Earlier, he had gunned down his grandparents.

"I had to climb over the school fence to escape with other friends," the girl, who the BBC is not naming, continues.

Her mother says the girl thought she might die. "[She said] 'I thought I'd never see you again'."

One 18-year-old student told Reuters he initially thought firecrackers were going off.

"I didn't think it was a gun at first," he said. "There were many shots: bang bang bang. Then it went quiet. Then it started again."

Metres from the school gates, paramedics loaded the wounded into ambulances and rushed them to hospital, as milling crowds hugged and cried.

Rescue worker Kiatikhun Verapongpradith rushed to the scene after hearing children as young as 12 had been hurt.

"I saw students who had been shot, some in the arm, some in the back, some in the chest. So I rushed to help get them to the hospital first," the 47-year-old rescue worker told Reuters news agency.

One grieving teacher told the BBC his friend was among the dead.

"She was my age. We went to this school together as students. Then we both became teachers at this school," the 31-year-old, who declined to give his name, said.

It is early days in the investigation and police haven't said anything about a motive.

They believe the 9mm handgun the shooter used belonged to his grandfather. Forensic officers found the gunman's shots to be "quite accurate", with several hitting "vital spots" on victims' bodies.

Others are filling some of the gaps. A teacher at the school has said the shooter was a good student - not aggressive and with good grades - and education authorities have described him as an avid gamer.

Prime Minister Anutin Charnvirakul said study pressures may have played a role.

"We learned that his grandmother was a teacher and she might have been strict with him. From what the police gathered from his close friend, they knew he was quite stressed about it."

It is clear authorities will have many questions to answer in the coming days - many of them about what change this crime must trigger.

Renewed calls for gun control reform

This is Thailand's deadliest mass shooting in years - and the second at a school this year.

In February, a head teacher and a female student were shot by an 18-year-old gunman during a school siege in southern Thailand.

Four years ago, a 34-year-old in the eastern Nong Bua Lamphu province killed 37 people, most of them preschoolers, in a shooting and stabbing at a nursery.

These crimes have resurfaced questions about gun control in the country.

"This shouldn't have happened," the boyfriend of one of the killed teachers told reporters, clearly distressed and trying to hold back tears.

More than seven million people are believed to own guns in the country, one of the highest rates of ownership in the world. Of those, more than one million are unlicensed owners.

While there are restrictions on gun licences in Thailand, people can still acquire the weapons - legally or illegally - with relative ease.

There is a thriving black market, aided by Thailand's porous land borders with four other nations. Problems with corruption and loose regulation in the police and military have seen weapons end up in the wrong hands.

Prime Minister Anutin said he had tightened regulations when he was interior minister three years ago - suspending new gun permits.

But gun crime remains rife, with deaths from gunshots among the highest in the region. And some in the community are calling for greater action.

"An act of violence in an educational institution, which should be one of the safest places in our society, serves as a stark reminder for Thai society to seriously and systematically review gun control measures," Natthaphong Ruengpanyawut, leader of the People's Party - an opposition party - wrote in a Facebook post.