They knew they might see things that will disturb them, but could not deter them from their duty.
He is carrying the briefcase as he enters the room, so still even in walking that he does not disturb the air around him.
The house is eerily pristine and immaculately preserved; your visit is the only thing threatening to disturb it.
c.1300, "to stop or hinder," from Old French destorber (Old North French distourber) and directly from Latin disturbare "throw into disorder," from dis- "completely" (see dis-) + turbare "to disorder, disturb," from turba "turmoil" (see turbid).
Meaning "to frighten" is late 13c.; that of "to stir up, agitate" is c.1300. Related: Disturbed; disturbing; disturbingly. Middle English also had distourbler (n.) "one who disturbs or incites" (late 14c.).