Why was this case tried in military court?

Another in the seemingly endless series. As reported here, an Indonesian military court tried this case:

The beating happened when HA and SKA, both 13, were riding pillion on a motorcycle driven by another friend, R. They passed [1st Cpl.] Saheri’s house in Cibinong, Bogor in West Java in December last year. The road was bumpy and when R tried to evade a hole, HA’s cup of ice tea flew at Saheri’s house, which was being renovated. 

During the trial, it was reported that Saheri exited the house, yelled at the three boys, screaming, “Thief! Thief! Thief!” while throwing rocks at them. 

In January, HA and SKA told a press conference at the Jakarta Legal Aid Institute that Suheri took them to a vacant lot near his house, tied them to trees and beat them. Locals who thought the boys were thieves also beat them, they said.

The prosecution had sought a four-month sentence; 1st Cpl. Saheri received an eight-month sentence from the three-judge court-martial. The report does not indicate whether the civilian assailants were tried in some other court.