！。。
Quiet! Everyone, don't move from where you are. We're starting a bag check now.
Literal
Quietly! Everyone that spot [object-を] don't-move-[negative-request-ないで]. From-now belongings-inspection [object-を] begin-[polite-ます].
A teacher or official taking control of a group. 静かに! is a bare adverbial command, with the copula and verb dropped — a typical one-word imperative for 'be quiet.' ~ないで as a negative request/command 'don't do X' is the negative counterpart of ~て. 持ち物検査 ('belongings inspection') is a fixture of Japanese school life — teachers sometimes check students' bags for contraband. その場 'that spot where you are.'