Malbim: For the action, he is not liable for murder or Eshes Ish, only for stealing Uriyah's wife. Regarding the doer, he is Chayav Misah, for (a) "I anointed you to be Melech Yisrael", and put Hashgachah on you, and saved you from all of your enemies - you should have remembered this, and been careful even from a small sin! (b) I gave to you great wealth (verse 8) - you are like the Ashir.