What happens to Rab and how does it happen? From chapters 11-12

When Johnny finds Rab at the tavern, the older boy is badly weakened by his wounds. Rab thanks Johnny for getting him the fine musket, although he never got a chance to use it before he was shot. Rab smiles and the young men have a warm moment of friendship. Rab asks Johnny to check up on his female relatives. When Johnny arrives at Silsbee Cove, no one is there––not even Grandsire, who had planned to sit out the battle at home. When Johnny returns to the tavern to report this news, Rab is dead. Dr. Warren says that Rab sent him on the errand just to get Johnny out of the tavern while he was dying.