Why didn't Tris just kill Jeanine?

Rating: 5/10 (14 May 2015)

Obviously, there probably wouldn't have been two more books/movies if Tris had killed Jeanine, but c'mon, really? It's not like she didn't have the chance to at the end of the movie to just shoot her instead of just knocking her out. It really annoyed me. Honestly, if I had just witnessed both of my parents dying, you better be damn sure the person who was responsible got theirs. Tris could have killed her and then in the second installment there was a new person who was set out to destroy divergents, fueled by revenge or something or just even sticking to the original reason of feeling threatened by them. The ending just didn't do it for me, and for that, I haven't watched the 2nd one. Perhaps, I may if I happen to catch it on TV, but other than that, with the ending of Divergent, I just wasn't interested to find out what happened next. Anyone else feel this way?