Masked gunmen forced their way into a jail on Indonesia’s main island of Java early Saturday and shot dead four prisoners accused of murdering a special forces soldier.

At least 17 gunmen stormed into the Cebongan prison in Yogyakarta and reportedly tortured several guards, forcing them to open the jail cell of the four detainees, local police chief Brig. Sabar Rahardjo said.

The prisoners were dragged from their cell and shot with automatic weapons before the gunmen destroyed surveillance cameras. The gunmen looked well-trained and fled just after five minutes of attacking, he added.

According to a source, the men were armed with AK-47 assault rifles and at least one pistol, and that they had threatened to knock down the prison door with grenades.

The shooting was allegedly provoked by the death of a member of the Special Forces Command, Indonesia’s elite military unit, after he was beaten and stabbed to death at a nightclub in Yogyakarta on March 19, reports AFP. Four suspects were arrested over the incident last week while three others remain at large.

National police spokesman Suhardi Alius declined to confirm whether members of the Special Forces Command were behind the attack.

“Whoever did it should be immediately arrested and prosecuted,” Djoko Suyanto, coordinating minister for Political, Legal and Security Affairs, told The Associated Press.