The time the letter was sent was half a year ago as well.
It could be that, the time when he sent the letter was before he met up with Paul and the others.
That time he might have thought there was nothing he could do, so he sent the letter.
It could be that he sent a similar letter to Paul as well.
However, soon after that, he met up with Paul and it ended just like that... that might be the case.
All of them are "might be possible".
I wonder what the actual case is, for I'm in a distant land, I can't even make a guess about it entirely.