Police plan to question a shooting instructor in the hope of learning about the motive that drove a teenage boy to go on a deadly shooting spree inside Siam Paragon shopping mall in Bangkok on Tuesday.
Investigators have obtained information about the shooting range where the 14-year-old went to practise and the instructor who supervised him, said Pol Maj Gen Nakharin Sukhonthawit, commander of Metropolitan Police Division 6.
The range is located at the Territorial Defense Command of the Royal Thai Army on Charoen Krung Road in Phra Nakhon district, according to Pol Maj Gen Nakharin.
After the Siam Paragon shootings, video was posted online showing the teen practising at a range in the presence of an instructor in military camouflage. The date when the video was taken is not known.
Pol Maj Gen Nakharin said officers would ask the instructor if anyone else was with the teenager on that day, and whether the boy used a rented gun at the range or brought a gun that he owned.
Shooting range regulations require people who are aged below 20 to be accompanied by parents if they want to practise shooting.
Hundreds of people ran screaming into the streets after gunshots rang out inside Siam Paragon late Tuesday afternoon. The young gunman was subsequently arrested at a furniture shop inside the mall after a rampage that left two foreign women dead and five other people wounded.
A source familiar with the investigation said the boy fired about 40 shots inside the mall. Eleven bullets were found in the dead and injured victims.
Forensic officers inspected the shooting scenes on the M, G, second and third floors and collected about 40 spent casings, mainly on the second and third floors.
The boy, who faces murder and other charges, on Wednesday was remanded to a juvenile detention centre where he underwent a preliminary psychiatric assessment.
The teen said very little and did not want to eat, but he did not ask to return home, said Nalinnart Krainara, deputy chief of the Department of Juvenile Observation and Protection.
The reaction could have been consistent with someone being in a place he was not accustomed to, she added.
His parents accompanied him to the detention centre.
In a related development, police inspected a business that produced BB guns and blank guns in Thung Khru district and was said to be linked to the shooting at the mall.
The suspect is said to have used a gun designed to fire blanks and had it modified to fire bullets. Three people were arrested on Thursday for allegedly selling a gun and ammunition to the teen.
Authorities have vowed to close a loophole in the law that does not classify blank guns as guns, meaning their owners are not subject to any licensing requirements.