An initial autopsy found no traces of drug in the body of the ex-policeman who went on a shooting spree that killed at least 38 people in the northeastern province of Nong Bua Lam Phu on Thursday, according to the national police chief.

Pol Gen Damrongsak Kittiprapas told reporters this afternoon that a second autopsy will be carried out to determine whether Pol Sgt Panya Kamrab was acting under the influence of drug when he went on a rampage at a day-care center in Naklang district.  Among those killed were 24 children, some as young as three years old.

He quoted the result of an autopsy conducted at Udon Thani provincial hospital as confirming that no traces of drug were found in Panya’s body. “The autopsy found no evidence that he had drugs within the 72 hours before the incident,” he said.

The police chief said Panya had a quarrel with his wife in the morning of the massacre.  “They had a quarrel and she called her mother to pick her up,” he said.

After the shooting spree at the day-care center, Panya returned to his home where he later killed his wife and son before committing suicide.

Pol Gen Damrongsak said Panya also had no record of mental health problems but had a history of drug use.    However, the police chief said on Thursday that Panya was apparently under stress and hallucinatedduring the deadly rampage.

He said Panya became policeman in 2012 with a clean bill of health. However, he quoted Panya’s mother as saying that it was possible that Panya resorted to drug use after he was posted back to his hometown in Nong Bua Lam Phu.  Panya had earlier served at two police stations in Bangkok.

Panya was discharged from the police force in June this year on charge of illegal possession of amphetamine.