That's a very good question.

We do know that some came with those plastic handcuffs. And one person (group?) actually did beat a policeman to death.

One big clarification I've learned from this batch of comments is that the most important problem is that the security failed. Regardless of anyone's intentions, if the crowd had not entered at all, there would have been no significant problem. So I am going to stop calling it an insurrection, etc., because it would have been a nothing-at-all if the security had held.

To put that another way, "intentions" of a group cannot easily be measured in a one-off like this because everyone has a different set to intentions. That is why security must hold: you never know what might happen if a crowd gets in somewhere. (And obviously they were not entering a public place, such as a shopping mall, where intentions might have to be analyzed, in retrospect anyway, if there were an attack.)