you were helping Dumbledore do something then Draco comes out of nowhere with his wand saying he has to kill Dumbledore but it's obvious he doesn't want to so then Snape come sober and points his wand at Dumbledore, Dumbledore is you grandpa and your only family

Snape: "AVADA KADAVERA" then Dumbledore falls off the tower and you scream Draco holds you back