most plausible explanation
If you were a hitman, could there be a more showy- off, f*** you, nasty way to kill someone?
"here's someone dead in a bag, with no way they could have got in themselves, and the police are going to fumble around for weeks eventually proving themselves to be totally impotent to find out what happened, how safe do you spies feel now?"
I fail to believe that a maths prodigy, spy, in a safe house, would have invited a random stranger to zip him up in a bag. It strains credibility.
I feel deeply sorry for him and his family, in my view he died for his country in the most horrible of ways and it is terrible the way his name has been blackened. Who among us would want our browsing records to undergo that kind off scrutiny.
How about a bit of sensitivity, el reg?