Some fairly obvious points need to be made about the killing of Denis Donaldson.
The first is that nothing happens in West Belfast without the knowledge and often the approval of the Provos. The idea that a senior and well known figure like Denis Donaldson could be killed by a small dissident republican group without the foreknowledge of the Provisional IRA is just plainly ludicrous.
In fact it is not stretching reality to suspect that this was an arrangement that suited both the killers and the Provos, the former because in their world they looked smart while the latter got rid of an embarrassing and possibly damaging leak. The real losers were Donaldson’s handlers, either the PSNI Special Branch or the British Army.
And make no mistake about this. Whoever pulled the trigger on Donaldson the real killers, the people who gave the go-ahead were the Provos
The Broken Elbow 
As always…
Isn’t there an argument that Donaldson was ‘surplus to requirements’ for the various elements of SIS who knew all about him, but his death would remove any potential future embarrassment, where interview or memoirs could implicate more senior agents, and / or senior bureaucrats or politicians, where, it being the way it is, they have a light touch but near total control of this society?
Wouldn’t want to embarrass anyone, would we?