A sergeant-major said to be mentally ill shot two colleagues dead and wounded another at the Army War College of the Army Training Command in Bangkok's Dusit district on Wednesday morning.
Special operations police were called the army college in Dusit district about 8.45am. Initial reports said one person had been shot dead and another wounded.
A spokesman then said the shooter was a mentally ill soldier who was threatening to kill 10 people.
Army deputy spokeswoman Col Sirichan Ngathong said later that the shooter was Sgt Maj Yongyut Mangkornkim, 59, an administrative clerk at the Army War College.
Col Sirichan said that about 8.45am Sgt Maj Yongyut walked into the administration office carrying a gun and opened fire.
SM1 Yongyut Mangkornkim, 59, walked out after the shooting inside the Army War College administration section in Dusit district, Bangkok, on Wednesday morning. An official recorded this from hiding inside the college building.
He killed Sgt Maj Nopparat Intarasunthorn and Sgt Maj Prakan Sinsong and wounded Sgt Maj Yongyuth Panyanuwat. All were administrative clerks in the same office, she said.
The wounded Sgt Maj Yongyuth was rushed to Phramongkutklao Hospital for emergency treatment.
After the shooting, Sgt Maj Yongyut left the college building. He was immediately arrested by police waiting in front of the Army Training Command.
An investigation would establish the motive for the crime, Col Sirichan said.
According to information from his office, Sgt Maj Yongyut was stressed and had health problems. He was on record as having suffered from mental illness.
Col Sirichan said those killed and injured would be well-taken care of. Police handling the case would receive full cooperation to ensure justice for all concerned, she said.
"The army would like to extend its condolences to the families of those killed and injured. It is a big loss to both the army and those families," she added.
In February 2020, a soldier shot dead 29 people in a 17-hour rampage and wounded scores more before he was shot dead by commandos in Nakhon Ratchasima province.
That mass shooting was linked to a debt dispute between gunman Sgt Maj 1st Class Jakrapanth Thomma, 32, and a senior officer, and the military top brass were at pains to portray the killer as a rogue soldier.