I can't really add much to the first article. My knowledge of the tactics of urban warfare go something like this:
- Try to avoid it.
- Seal off the area so it doesn't turn into a meat grinder like the Russian front in WWII.
- Stay out of the streets because that's where the enemy can shoot you best. If necessary use explosives to knock down walls to facilitate this.
- Don't hug the walls. They may provide cover and make you feel safe, but they are also bullet and fragment traps because of ricochets and reduce your freedom of movement.
Hopefully due process will be followed and he will be exonerated if that is the case. Marine Colonel Jeff Cooper once said that the good thing about military courts is that they tend to care more about finding out what happened instead of placing blame. Hopefully that means the marine won't spend the rest of his life in prison for a split second decision when his life was in mortal danger.
UPDATE: Several people are writing about how the Geneva Conventions were being violated by the marine. This is incorrect. Firstly it is against the conventions to occupy a mosque, so they don't apply to this specific case. Secondly, the conventions don't protect non-uniformed insurgents like those in Iraq anyway. Russia made sure this was the case before they signed the conventions. The Volokh Conspiracy has further analysis.