Well what I did was I went into the room and killed everyone except the Blue boy.Then I MC the blue boy to run out into the hallway (without pulling any levers).Then got him to the safe point with another blue boy.Then when the ring passed i ran him to the nearest door and got him inside and pulled that lever.And i did the same with the next.AND the next untill only one remained so kill the blue boy however you like and pull the last lever.
PS:I did it on easy.
Hope this helps
Oh, I beat it before you gave me help. I figured it out right after I asked for help yesterday.