I suspect it was just fire hoses, but it makes little difference to the people facing the water jets. Many sources conflate the two. For a picture of firemen (not policemen) using the hoses, see here. For another picture, captioned "water cannon", see here - but remember that the reporters often (in fact invariably) don't write the picture captions - that is often done after the reporter has filed the story. I'll change our caption to "high-pressure water jet", which leaves vague what is producing the water jet.