A military ranger was shot dead and her mother and two children wounded when their car was ambushed in Pattani's Sai Buri district yesterday.
Police said insurgents may have carried out the attack, but it could have stemmed from a personal conflict.
The attack took place on a local road in Ban Joh Batu in tambon Thung Kla around 10am.
Cpl Anastasia Malee, 31, of the 44th Rangers Regiment, was found dead with gunshot wounds to her torso and head in her Honda City.
Cpl Anastasia's 55-year-old mother Maeyae Arsae, son Sharif Wama, 9, and daughter Iffara Wama, 11, were also shot. They were sent to Somdej Phra Yuppharaj Saiburi hospital.
Doctors at the hospital said the three have since stabilised.
Police said Cpl Anastasia was driving to a relative's house when two men approached on a motorcycle. One of them opened fire at the car with a 9mm handgun.
The car stopped and the attackers opened the car's door and shot Cpl Anastasia in the head. The assailants also stole Cpl Anastasia's gun, police said.
Police found five spent bullet shells in the car and three fired bullets. They also examined the car for fingerprints and looked for DNA samples.
Police said insurgents may have been responsible for the attack, but they have not ruled out jealousy.
Cpl Anastasia earlier fought with her estranged husband Aduenam Wama, police said. Mr Aduenam was sacked from a ranger position about three months ago and Cpl Anastasia recently moved into a new house. Police are looking for Mr Aduenam and intend to question him.