A 14-year-old suspected gunman has been arrested. Video footage showed a long-haired boy wearing a black shirt, glasses and a cap being taken into custody.
National Police Chief Torsak Sukvimol told reporters that the boy was too confused to undergo questioning.
“He is a mental patient at Rajavithi Hospital and he has not been taking his medication,” Torsak said.
“He said it was like there was another him telling him who to shoot.”
A private school called The Essence, just metres from Siam Paragon, confirmed the suspect was one of their students and offered condolences to the victims’ families.
“We will collaborate with the authorities and investigators for the benefit of those involved,” Wiwat Catithammanit, director of the US$4,000-a-term school said in a statement.
The upmarket Siam Paragon, located in the heart of Bangkok, is one of the Thai capital’s top shopping destinations, hugely popular with tourists and Thais alike.
The mall draws crowds with its high-end stores, aquarium, movie theatre and dining options.
In 2013, it was named the world’s most photographed place by Instagram.
Hundreds of people were earlier seen rushing out of the mall into the pouring rain.
“Actually I was outside of the mall but suddenly a lot of people just run away and I thought (it is) because of this rain,” said South Korean tourist Pepper Park.
“And then some Thai people told me we should run away. I asked why and they said because there is some terrorism.”