This dream may be an emotional restoration dream or it may be a warning about a quarrel (argument) between you and this man (if he represents another person or the color of his skin, just apply those meanings). Both the knife of glass and the rifle symbolizes words of criticism or insults.
The fact that he stabbed you from behind speaks of him causing you a lot of harm with words of criticism and insults behind your back (discussing you with other people). The deep slashes and stabs speak of him not holding back. He wants to harm you and your reputation big time.
Glass is “see-through” and often speaks of “spiritual insight” (the opportunity to see into the spiritual realm), so this could mean that he feels that he received some spiritual insight and that the words of criticism and insults are therefore justified and true.
The bullets that you shot him with are also words of criticism or insults but it appears to be old (not valid anymore like the proverbs: revive old differences or chew the rag). So if this dream is a warning of an incident to come, you may have to address the incident differently (at least use better words, or ask God how you should address this incident) and/or you should pray about this so at to [prevent the incident from happening.