It does not make sense why kill Loureiro.

Sorry, but it seems very brittle as a story.

The answer is, no one can know for sure.

The most probably answer from the facts we have is quite simple and human... Jealousy. They both were classmates in the same overseas undergrad program, Nuno was a well established and accomplished professor in one of the preeminent tech schools in the world. While he flunked out of his program, and hasn't done much of note.