Sammy: Guilt trips everyone until they let him go.
Darius: Distracts them with idle chatter and philosophical questions. (eg - Do the needs of the many outweigh the needs of the few?) Then disappears.
Ben: The place is blown up and he's gone (also, where does he get these explosives?? Does he have a stash in his pocket??)
Yasmina: She's left and "Haha, losers!" is written on the wall in what could be either lipstick or blood. Who knows?
Brooklynn: Nowhere to be found and a letter telling them to make better life choices is in her place.
Kenji: He's gone, and when everyone tries to find him, he's in the doorway and sticks his tongue out at the kidnappers and runs away.