Seven people are dead in Thailand Friday after a teenager went on a shooting spree at his school outside of Bangkok. 

Police said that a 14-year-old boy used his grandfather's gun to kill two of his grandparents. The rampage continued at his high school north of the Thai capital, the Wall Street Journal reported. 

At the school, the shooter killed two teachers and three school staff before turning the gun on himself, police said. He was pronounced dead at a local hospital. 

Nine other people were in critical condition following the attack, Thailand's defense minister said, while 20 others sustained minor injuries.