A 16-year-old gunman, apparently seeking revenge for the shooting of a friend, opened fire in Nakhon Si Thammarat on Monday night, resulting in one death and three injuries, police said.

Police were alerted to the shooting in the Ban Kong Sai community at around 6.30am on Tuesday.

They found a man identified only as Phuwarat, 23, lying in a pool of blood with a gunshot wound to his head inside a makeshift shelter. The victim had died on the spot.

The three injured men were taken to Thung Song Hospital.

The initial investigation found that the victims were resting in the shelter when two men on a motorcycle arrived in the middle of the night. One person remained with the bike while the other, armed with a gun, entered the shelter, firing then fleeing the scene.

During questioning, the deceased’s girlfriend said that he had mentioned a threat of an attack in a recent chat conversation but did not provide details.

Later on Tuesday, police apprehended a 16-year-old Mathayom 5 (Grade 11) student, and seized a gun believed to have been used in the shooting.

Further investigation uncovered a long-standing feud between the two groups, which escalated from social media disputes to gun attacks.

The incident was believed to be retribution following an earlier shooting in which a 15-year-old friend of the assailants was injured, police said.

Police are still looking for the remaining suspect.