Thai police have arrested four men believed to have sold a gun to a schoolboy accused of carrying out a deadly mall shooting at a shopping mall in Bangkok this week.

The suspects reportedly arranged the deal in private chats over messaging app Line to supply a modified blank gun to the fourteen-year-old for 16,000 THB (433 USD). They then allegedly deleted the conversations after the sale was made.

Suwannahong Pramkanajan, 44, and his son Akkarawich Jaithong, 22, were arrested in Yala province, while Piyabutr Pianpitak, 31, and another unnamed individual were nabbed in Bangkok on October 5. All of them were being held in police custody.

Officers said they also seized from the dealers hundreds of blank bullets, two bank books, nine ammo magazines, narcotics, and tools used to modify firearms.

Police Major General Noppasin Poolsawat, Deputy Commissioner of the Metropolitan Police Bureau said: 'The father and son said they have been manufacturing and selling blank guns for one to two years. They made no effort to verify buyers' ages during these transactions. The police are currently attempting to trace the buyers of these weapons.'

Suwannahong claimed that he had previously warned his son against illegally selling guns online, but said his warnings had been ignored. He told local media: 'I did not know my son had sold a gun to the 14-year-old boy. I only knew he was using my bank account to receive the buyers' payments.'

Authorities said the suspects are facing charges of possession and sale of firearms and ammunition without proper permits.

On Tuesday, October 3, the teenager allegedly barged into the upmarket upmarket Siam Paragon shopping mall in Bangkok and opened fire on shoppers, killing two and injuring five others.

Police Chief General Torsak Sukvimol had said the suspect will undergo hospital checks this week to assess his psychological state.

The youngster is facing charges of murder, attempted murder, possessing a gun without permission, carrying firearms in public and firing a gun in public.

It comes almost a year to the day when gunman Panya Khamrab, 34, killed 36 people and injured 10 others in a rampage at a nursery in Nong Bua Lamphu province in the north of the country on October 6, 2022. He later turned a gun on himself during the spree.