Why did knights watch kill Jon Snow?

Related questions

1. Does Sansa marry Tyrion?
2. How did Olenna die?
3. How did they get the poison in Joffrey's Cup?
4. Why did Olenna poison Joffrey?
5. What happened to Cersei's daughter?
6. What age is Sansa Stark?
7. When did Olenna put the poison in Joffrey's Cup?
8. Does the Prince of Dorne die?
9. How did Lady Olenna die?
10. How did baratheon die?

Tags

1. #death
2. #betrayed
3. #announced
4. #penalty
5. #nights
6. #books
7. #stabbed
8. #because
9. #going
10. #wildling
11. #south
12. #shieldhall
13. #break
14. #winterfell
15. #speech
16. #watch
17. #breaking
18. #night