Here is the most recent piece of news I could find (in German only, sorry but English is not an official language of Kanton Basel
):
Flughafenlotsen-Mörder weiterhin spurlos verschwunden - News Basel: Stadt - bazonline.ch
As of May 7 the prime suspect, Karim Quali, is still at large and nobody even knows if he's still alive.
Cheers,
Dg800