the letter part of the letter about Sawyer's death was built off a little passage in LtH where Bush thinks about the oddness that the spanish tied buckland up and left him unharmed while they "savagely" cut sawyer's throat. in the letter HH admits that he thought the chaos was the perfect time to get rid of sawyer, and knew that wellard would help him. his reasoning was something along the lines that if sawyer reached shore alive (since he seemed to be recovering a bit) then the surviving lts would all be hung for mutiny, and he wasn't going to let that happen, so sawyer had to die (the letter is better worded than that, but essentially the gist). so he either suggested to wellard or ordered him (can't remember which) to go kill sawyer (i think, don't quote me). and later when bush reads about wellard drowning he puts the question HH again he he gets all weird again and won't give an opinion on wellard drowning.