Out the top of my head, the ones indicted for the murder of Sal Montagna are Raynald Desjardins, Vittorio Mirarchi, Calogero Milioto, Jack Simpson and Felice Racaniello.

The French articles on his death provide the best information;

As of this moment Montagna is considered the number one suspect for the murders that took place. It is is thought that he tried to take out Desjardins too, who miraculously survived the hit without any injuries. Beforehand, Montagna, the Arcuris and Desjardins worked together, but at some point they had a falling out, which is thought to have occured at a meeting in September 2011. Only two weeks later, Desjardins was shot at close to his home, but the bullet somehow missed his head by a few centimetres, based on the bullet hole in the window. The would-be assassins fled the scene in a sea doo.

Then a month later a supposed accomplice of Montagna, Lorenzo LoPresti, was murdered while smoking a cigarette on his balcony. A month after that Montagna was apparantly lured to a meeting by Jack Simpson, which turned out to be a set-up. And while he succeeded to jump through a window, Montagna died shortly after due to being shot at least once. By decrypting text messages (probably with the help of Montagna's cell phone) the police were able to link Montagna's murder to Desjardins and co.

If the set-up would not have failed so miserably as it did, we would know probably still be wondering what exactly happened to Montagna and who was behind it.