Military base, killed soldier and sadistic officer - mysterious episode

Again, I'm looking for an old episode of TV series - I can't find it for at least 25 years. I'm pretty sure it's something filmed in the 80s or 90s and the action was contemporary (so any of those decades, no futuristic, wartime or 19th century vibe). I'm practically sure by now that it wasn't a prison of any kind, otherwise I would have found it a long time ago, and I've checked all the well-known as well as lesser-known films on the subject and there isn't a single even similar scene - except for “Sentenced to Shawshank,” but there it looks completely different and is in the middle of the film, not at the beginning.

The two friends were in some kind of penal military unit or something like that. Getting to the point: two colleagues are in this “army”. One of them is released on some sort of furlough. I remember that the officer clearly tells him that he can go home, so the tall, well-built guy gets up and walks down a long corridor (perhaps past some photocell door). He walked with a confident stride, even towards the viewer probably. At one point he gets shot in the back and dies on the spot. Then the officer says to the other guy, “You're going to get tired.”

Probably an episode of “JAG” (so says another person, who also associates such a motif from this series) or “MacGyver”, not any episode of “Texas Ranger” rather. Perhaps this will somehow guide, although I doubt it - I've been looking for 25 years at least.