I just heard about this. My condolences and deepest sympathy for the victims.
Reports suggest the shooter was a soldier who was having a land dispute with his CO. The CO was the first to be killed. The shooter then went on a killing spree, on the streets, then at a shopping mall. The shooter was eventually killed by the Thai security forces.
Thailand is now in mourning for the deceased. May the rest in peace.
Source – Sky News Australia