There was no immediate danger, i think it was a Code-1 type call and they were just going to have a look and knock on doors, etc. Like you said, if they were 'Low level crime officers' they would have more than citizen's arrest powers, and carry a weapon such as a telescopic baton probably. By the way, the van was not loaded with riot shields, i believe it just served as a carrier but happened to carry a cage thingy for safety.