A 14-year-old killed his grandparents at their home before carrying out a deadly shooting at his school in Thailand on Friday, police said.The teenager opened fire at Debsirin Nonthaburi School in Nonthaburi province, just outside Bangkok, killing several people and injuring at least 30 others – including nine in serious condition – according to Thai police. He was reportedly targeting teachers. The shooter, who lived with his grandparents, later killed himself, Nonthaburi provincial police commander Lt Col Dechrapee Kongdee told Reuters. (Reuters)The number of casualties was at least eight, including the suspect and his grandparents, though nine others were said to be in critical condition on Friday evening. Speaking at the scene, Thai prime minister Anutin Charnvirakul said the shooter had “more than 30 bullets left” when he ended the attack by shooting himself.“Police interrogated his close friend who said the suspect had been under stress,” related to his schooling, the prime minister told reporters outside the secondary school.His actions suggested the shooting was “well planned” with “clear steps and clear goals”, Mr Charnvirakul said.One teacher told BBC News that the suspect, who was in year nine at Debsirin Nonthaburi School, was a “good kid with good study records”, adding that the suspect was not known to be aggressive. (AFP/Getty)The shooting began at around 10am local time. At the time, police urged students and teachers to shelter as the attacker remained inside the school. Police said he fired 26 rounds, while another 34 rounds of ammunition were found at the scene.A fellow student who survived the shooting told the BBC: “I couldn’t see anything but a [cloud] of dust. He walked from room to room. My desk was very close to the teacher. I had to climb over the school fence to escape with other friends.”Police take away computers from the home of a student who shot several people (AP)Lt Col Kongdee said earlier that the suspected shooter was 14 years old. He was described as an “avid gamer” by Thailand’s deputy interior minister Polapee Suwanchawee, based on evidence police had gathered at his home.According to the Bangkok Post, investigators found the bodies of the suspect’s grandfather and grandmother, both with fatal gunshot wounds to the head. (AFP/Getty)Authorities believed the killings happened before the school attack, although the exact sequence remained under investigation, local media reported. Police later confirmed that the suspected shooter had died from an apparent self-inflicted gunshot wound. A first responder said the shooter was still alive when they arrived at the scene, but died on the way to the hospital. The suspect was armed with a 9mm handgun, which Thai media reports described as belonging to his grandfather. He had posted a picture of the gun on his Instagram in April, according to preliminary information. Police were examining the weapon, interviewing witnesses and investigating the circumstances surrounding the attack.