Related Clues:

• Sentry's directive
• Cop-show broadcast
• Drill command
• Perimeter command
• Black-and-white flash?
• Sentry's word
• LAPD alert, e.g.
• Killer-on-the-loose alert, perhaps: Abbr.
• PD alert
• "Be on the lookout" letters
• LAPD announcement
• ''Don't take another step!''
• Stop temporarily
• PD notice
• Patrol car broadcast