Why did Night's Watch kill Jon Snow?

Related questions

1. Is ygritte Tormund's daughter?
2. Who said you know nothing Jon Stark?
3. What did Ned whisper?
4. What did Ned Stark whisper before death?
5. How many times does ygritte say you know nothing?
6. Is Jon Snow dating ygritte in real life?
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Tags

1. #stabbed
2. #outside
3. #simple
4. #finale
5. #decided
6. #rationale
7. #south
8. #lured
9. #murder
10. #night
11. #quite
12. #traitor
13. #wildlings
14. #watch
15. #setup