It is difficult to decide whether this verse deals with what the Gentiles will do or whether it speaks in more general terms about what will happen to Jesus (be it from the side of the Jews, the Gentiles, or both). The mocking takes place before Pilate (Mark 15:20), but also by the chief priests and scribes at the cross (Mark 15:31). The flogging happens before Pilate (John 19:1); the spitting both after the nightly meeting of the Sanhedrin (Mark 14:65) and before Pilate (Mark 15:19). The killing is an action not only of the Roman soldiers who crucify him, but also an event resulting from the activity of the Sanhedrin—it is not for nothing that Pilate gives Jesus once again over to the Jews (Mark 15:15)!1
34 And they will mock him and spit on him, and flog him and kill him. And after three days he will rise.”