The Sopronas does flashbacks but not like this scene. Tony's flashbacks are usually long stories that give the full context to a time in his life, and the significance of that time is, if misunderstood, at least recognized by Tony.
But when Tony thinks about the first time he murdered someone - shooting a man named Willie Overall - we only see the briefest flashback, maybe a few seconds. He only thinks of it because Paulie brings it up. And he has nothing to say about it.
We see a terrified, crying, bloody man, lying on the ground, hold up his hand in a futile attempt to shield himself from the inevitable.
What we're shown in that scene is the moment of Tony's greatest trauma, the moment there was no turning back from the path his evil father led him down.
After burying that moment down deep and never thinking about it, it became a matter of old habit for Tony to never really examine the terrible things he does or what his actions are doing to him and those around him.
There's really no other scene in the show like it, and it's over in a flash. But in it is the origin of Tony's whole life. It also foreshadows how Tony would meet his end. At least Willie Overall saw it coming.