The flags will be lowered Friday in tribute to Christopher Reeves.
The 40-year-old Millville officer died early Sunday when a driver - who allegedly was fleeing from police - collided with his police cruiser. The driver - who faces numerous charges - and another Millville officer were seriously injured in the accident.
Reeves' survivors include his wife, who also is a Millville police officer, and their 2-year-old son.
Guadagno - who is serving as the state's chief executive while Gov. Chris Christie is out of state - issued the directive in an executive order she signed Wednesday.