They were driving like ****s prior to the RR incident. 
  
http://www.liveleak.com/view?i=3cd_1380579664 
  
Pulling wheelies, running red lights, driving on the footpath, erratic lane changing, driving into oncoming traffic etc 
  
 
  
  
  
From what I can tell a lot of the bikers had their plates removed, which suggests they planned on driving like ****s and wanted to avoid detection