This is the third film of 2018 where John David Washington plays a cop. The other films were "BlacKkKlansman" and "The Old Man & the Gun".
The police announcement to disperse, made to the crowd of protesters, is done using a Long-Range Acoustic Device (LRAD), which uses uncomfortably-high decibel sound to break-up crowds. Its piercing ringing sound would be much, much higher than depicted, however.
Rob Morgan (Will) & Cassandra Freeman (Lisa) played on the Netflix series "Luke Cage". Rob's character Turk also starred on several other of the Netflix Marvel shows.
Jasmine Cephas-Jones also starred with Hamilton co-star Daveed Diggs in Blindspotting, another film about the shooting of an unarmed Black man by police.
Kelvin Harrison Jr. and John David Washington both appear in Monsters (2018).