There's a popular opinion, that a famous Danish king Harald Bluetooth died as a result of taking an arrow, well... straight to his rectum. Not only have I encountered said story over the Internet on numerous occasions, but even read it in print: firstly, in Erik Roth's "With a Bended Bow" and then in Jim Bradbury's "The Medieval Archer". And both times with no reference to the source. So I searched, but couldn't find any historical text that would suggest it. Saxo Grammaticus writes that Palnatoke killed Harald while the latter was sitting in the bushes, emptying his bowels, but doesn't specify the nature of the fatal wound. Another source that gets thrown around a lot is "Jómsvíkinga Saga", but it just says that Harald was shot while resting at a campfire in the woods. Snorri Sturlusson's "Heimskringla" just mentions Harald dying from the wounds sustained in a battle with his son. Now I'm curious, is there any real evidence of the fabled butt-shot, or is it merely a modern myth?
I can't find any evidence of Harald being shot in the back (other than figuratively). In fact, the only roughly contemporary account of his death that I can find in some casual searching is from the Chronicon Roskildense probably written in the 12th century. Note that the Chronicon was likely the earliest "history" as opposed to "saga", although being written over 200 years afterward the lines between the two are pretty blurry.
The account of Harald's death is simply this:
Quibus fidens/ dum Haraldus per siluam licencius vagaretur, Tokko, eum videns, in vlcionem iniuriarum sibi factarum cum sagitta eum letaliter vulnerauit. Qui rediens in Slauiam mortuus est, atque Roskildiam delatus in ecclesia, quam ibi edificauerat, gloriose est sepultus
My Latin is attrocious, but very roughly (if anyone can give a better translation, please don't hesitate) it translates to this:
While Harald wandered through the woods freely, Tokko saw him, and in vengeance for the injustice that had been done him, fatally wounded him with an arrow. He returned to Slauiam and died, and was carried in the church in Roskilde which he had built, and was buried with honor.
For the adventurous, the full text is available in Latin here.
Aside from that and the sources you've already located, I'm doubtful that you'll get any closer to anything conclusive unless somebody locates and exhumes the body.