from the window in his office , he heard first , then saw the white toyota pickup reverse at tremendous speed , a screech of brakes , maybe a scream ( but he was not sure of this fact ) , then silence ( he knew this to be certain ) , followed by a simple spray of ephemeral dust , the very dust that now stuck in his memory , the way it stuck to the skin in the harsh harmattan winds that blew through the streets of monrovia in december .