Led by Bowen Marsh, the group mutinies against Jon in the snow. The first to strike is the steward Wick Whittlestick. Jon manages to disarm him, but he is stabbed in the stomach by Marsh.

Why did Olly stab Jon?

Olly sought refuge at Castle Black after his parents were killed by wildlings. Their murder left him angry at the band of nomads, so when Jon defended them in season five and granted them passage past the Wall, Olly felt personally betrayed. He helped slay Jon in a mass stabbing, but he later paid for it with his life.

Why did they stab Jon Snow in season 5?

Snow was killed at the end of season 5, after his ideas about what to do with the Wildlings and his stories about the White Walkers drove the rest of the Night's Watch past their breaking point. He was labeled a traitor, and just about everyone at Castle Black had a go putting a knife in his gut.