"Bulls on parade!" - North American metaphor slang,
Usually used to notify those around you that police officers/soldiers are present and/or taking action nearby, and that it may be time to defend yourself against them.
"Bulls on Parade" is also a song by the band RAGE AGAINST THE MACHINE, which features on the Album "Vietnow". The band often uses this song as an opener as it is very exiting and contains powerful anti government rhetoric.
"oh shit watch out man, they're coming... YO! BULLS ON PARADE!"
RATM: "Arms warehouses fill as quick as the cells,
Rally round the family with a pocket full of shells,
...BULLS ON PARADE!"