Why is this case being sent to a military court?

The case of a Russian teen who killed a police officer and a teacher and took hostages is being sent to a military court for further proceedings. Why? Here is RAPSI's report:

The Moscow City Court Presidium on Friday revoked a ruling ordering Moscow school student Sergey Gordeev who shot two people in February 2014 to undergo psychiatric treatment, RAPSI reports from the courtroom. 

The case will be reconsidered by the Moscow Regional Military Court as Gordeev in particular stands charged with hostage taking. The teenager can get a prison term. 

The incident took place on February 3, 2014, when Sergey Gordeev, 15, brought a rifle and a carbine to school. He killed a police officer and a teacher, injured one more person and took hostages. 

The Investigative Committee found that the student fired at least 11 times from the small caliber rifle before he was arrested. 

The teenager partially admitted his guilt. The psychiatric evaluation showed that he is mentally fit. Last summer, the Moscow City Court confirmed the original court’s ruling that the student undergo compulsory medical treatment. 

In late September, relatives of victims filed a cassational appeal with the Presidium of the Moscow City Court. They requested that the original ruling of the Butyrsky District Court be overturned as well as the ruling of the Moscow City Court in the appeal. They wanted the case to be returned to the court of original jurisdiction for a review starting from initial proceedings.

It seems from this account that hostage-taking charges alone bring the case within the jurisdiction of the military courts.