^^^^
According to Radio-Canada reporter Pascal Robidas,

1. the Sûreté du Québec (province's police force) has indicated that Salvatore Scoppa's murder was retaliation for his having ordered the four murders, and

2. the SQ had found the motorcycle used by two of the shooters.

I don't know when the motorcycle was found, especially in light of the fact that last month, the SQ had published photos for the first time since Sollecito was killed, including a picture of two unidentified people on the motorcycle.