This is a type of emphatic expression. It can be translated as "great excitement" or "a lot of excitement." (See: [[rc://en/ta/man/translate/figs-litotes]])
## excitement ##
This refers to negative excitement such as distress, extreme anxiety, fear, or confusion.
Possible meanings are 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."
## he questioned them and ordered them to be put to death ##
"Herod questioned the guards and commanded soldiers to kill the guards"