Police Dispatcher here,
Usually these happen whenever an Officer screams for help or when there are calls for a shooting in progress or something else high priority that requires a perimeter set-up.
Recently there was a pursuit turned stand-off on the interstate that had a lot of officers on-scene: https://imgur.com/LjWHtLt
15 IF PLANTS COULD TALK OF THE CREEPIEST THINGS THEY WOULD SAY
19 SOMETHING YOUR EMPLOYER DID THAT INSTANTLY KILLED EMPLOYEE MORALE
28 IF YOU SUDDENLY CAME INTO THE POSSESSION OF 20 TONS OF NUTELLA WHAT WOULD YOU DO
20 WHAT MOVIE WOULD 10X BETTER IF YOU ADDED DINOSAURS
18 WHATS A KILLER FIRST DATE IDEA
17 CONSUMERS SOMETHING A BUSINESS WILL DO THAT WILL INSTANTLY TURN YOU AWAY FROM DOING BUSINESS WI...
13 SOMETHING THAT YOU HAVE PURCHASED IN THE PAST BUT HAVE NEVER USED ONCE SINCE THEN
22 SOMETHING YOU THOUGHT WOULD BE EASY UNTIL YOU TRIED IT