Laura Jedeed, "What I Saw in #LA Wasn’t an Insurrection. It Was a Police Riot."
https://www.thenation.com/article/activism/los-angeles-protest-police-riot/
Jedeed doesn't mention a notable earlier use of the phrase "police riot" in the US. So let me inject a bit of history.
I remember the violence in the streets at the 1968 Democratic National Convention in Chicago.
https://www.thecollector.com/chicago-riots-1968-dnc/
I was even indoors at the convention at the time. My step-father was a delegate and I attended on a guest pass.
The National Commission on the Causes and Prevention of Violence asked Dan Walker to lead an investigation into the violence. He and 200 staffers studied film footage, reviewed FBI reports, and interviewed more than 1,400 witnesses. In the end, the "Walker Report" referred to the police violence against protesters, journalists, and bystanders as a "police riot".
http://archive.org/details/rightsinconflict0000walk/page/n5/mode/2up
Walker was no radical. He was a Naval officer, Korean War vet, executive at Montgomery Ward, campaign chair for Adlai Stevenson III, and Governor of Illinois, 1973-77.
https://en.wikipedia.org/wiki/Dan_Walker_(politician)