Who mailed the envelope to The American?

I'm curious who people think did that. That its not really explained isn't anything I consider a fault or "plot hole" (such an overused term). I'm okay with stories that require some imagination to connect the dots.

To be clear, I'm referring to the envelope with the article about the three dead people in Sweden. It's given to Clooney's character by the cafe worker who says "a letter from a friend". I can think of three possibilities.

1. Pavel - seems the most obvious. Maybe he's just keeping his employee in the loop. Or maybe it's to let him know that he knows where he is staying. They'd already talked about what happened in Sweden, so I'm not sure why Pavel would feel the need to bring him up to speed on that, but it could be to show that its unsolved and there are no (reported) leads.

2. The Swedes - we never find out why the initial attempt on Clooney's character is happening. Why is there a hit on him? Maybe it's related to a job he did in the past. Maybe its personal, and they want to taunt him to let him know they are coming and he can't get away. Possible.

3. The Priest - this is a longshot one. But possibly The Priest heard about events in Sweden and made some connection to Clooney's character. Maybe he wants to remind him of his past to try and offer a change of life. I do think the Priest is genuine in his attempt to save Clooney. The Priest knowing about what happened there seems a stretch, but its possible.