If the army starts shooting its own soldiers, it's not going to exist for very long. You can read very obscure stories about occasional killings during the Vietnam War, but those are almost always things that happened in the jungle when nobody would ever find out.

If they try that kinda thing in Israel today, it's not going to be a secret, and all of the other infantry and their family are going to wonder who is next, which in turn would massively reduce support for the Israeli military.

No he would sit in a jail cell. As a trained soldier no one would fuck with him

Essentially a perfectly risk-free environment. But he chose murder instead