researchers divided those involved into 4 categories:
* watchers - present at riots but only observed what was happening; some were bystanders but others came to watch on purpose
* rioters - actively involved in violence; some thrill seekers but some upset about initial shooting
* looters - broke into shops or stole goods; some were opportunists and others were sellers wanting to maximise own profits
* non involved - didn't take part; some wannabes and others chose to stay away