Military police in Siem Reap said they suspect another man was involved in an acid attack on a woman and her son for which three people have already been charged.

Ngim Siha, chief of military police in Siem Reap province, said on Monday that authorities have the identity of a fourth suspect believed to be connected to the December 26 attack.

On that night, police say a group of men allegedly tossed corrosive acid on Yi Oun, 40, a widow, and her son, Nuon Chivoan, 19, in Siem Reap Town’s Sala Kamroeuk commune.

Major Mok Sam On, Deputy Chief of Siem Reap Town Police, said Oun is still in the hospital and her condition has yet to improve. The chemical substance left her unable to speak.

It was the second acid attack in less than a week.

After the first, which took place in Sihanoukville and left a woman dead, the suspect fled somewhere near the Thai-Cambodia border, said Chet Vanny, a deputy police chief in Sihanoukville.

To contact the reporter on this story: Sen David at [email protected]