Why has this case been referred to a military court?

A retired Russian officer, already serving time on an earlier charge, has been referred to a military court on charges that he sent a video from jail urging others to engage in acts of violence. The Russian Legal Information Agency (RAPSI) has the story of Col. (R) Vladimir Kvachkov here.

According to case papers, Kvachkov, who is serving his sentence in a Mordovia’s prison, made a video appeal via his cellphone in 2015. Investigators believe that other inmates sent the video “to email of persons at large.” These people later posted it on the Internet. 

Experts found that the video contained linguistic and psychological elements of inciting the public to violent coup and acts of violence against Russian authorities, the statement reads.

The exercise of military jurisdiction over retired military personnel violates contemporary human rights norms. Could this case not have been tried in a civilian Mordvinian court?