There's another possibility: Alex could be a Scientist (like the other roles mentioned), but in that case, he was killed by the Cop, which is why the text mentions an unknown person, as the Cop is an outsider. So, it might be a hint about his role, or it might not be. But where does the Mafia kill come in? Poison or Night? It's unlikely that the Mafia would block their own member, especially a killer, so I don't consider Wolfie in this case.
So, either Alex is a Mafia member, and they wanted to deflect suspicion from him (unlikely), or Alex is a Mafia member who was killed by the Cop, or Alex is a Town member who was killed by the Godfather/Cop, or Alex is a Copycat who was killed by the Cop. The last option seems somewhat more likely due to the Cop's "mana search."
A kill by the Mafia? But wasn't Vesper killed by a Barbarian? "Free action after killing the twin" is indeed a block, not a kill. I don't see any arguments in favor of a Copycat kill yet.
Added 1 minute ago
I'm not making a table yet because, in fact, any action in a turn can be attributed to mana, which means that it's simply impossible to eliminate anyone.
Elizer Yudkovsky, "HP and the Methods of Rationality".
Мой ник транслитерируется по-разному, но я предпочитаю варианты Оот и Ооот.