This phrase is used to emphasize what really happened. This could be said in a positive way. AT: "there was a great disturbance among the soldiers over what had happened to Peter" (See: [[rc://en/ta/man/translate/figs-litotes]])
The abstract noun "disturbance" can be expressed with the words "disturbed" or "upset." AT: "the soldiers were very disturbed about what had happened to Peter" (See: [[rc://en/ta/man/translate/figs-abstractnouns]])
Possible meanings are that 1) "when Herod heard Peter was missing, he went himself to search the prison" or 2) "when Herod heard Peter was missing, he sent other soldiers to search the prison."